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Performance, combustion, and emission characteristics of DI diesel engine using mahua biodiesel
C H A P T E R
12 Performance, combustion, and emission characteristics of DI diesel engine using mahua biodiesel A. Santhoshkumar, Vinoth Thangarasu, R. Anand Department of Mechanical Engineering, National Institute of Technology, Tiruchirappalli, Tamil Nadu, India
O U T L I N E 12.1 Introduction
292
12.2 Selection of feedstock
293
12.3 Oil extraction
294
12.4 Transesterification
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12.7.3 Engine and fuel modification 12.7.3.1 Forced intake air pressure 12.7.3.2 Fuel modification 12.7.3.3 Engine modification 12.8 Engine exhaust emissions 12.8.1 Formations of emissions
12.5 Chemical kinetics of biodiesel production from inedible seeds 296 12.6 Physicochemical properties of SVOs 12.6.1 Chemical characterization 12.6.1.1 Fatty acids 12.6.1.2 Phospholipid content 12.6.1.3 Waxcontent 12.6.1.4 Peroxide value 12.6.2 Physical characteristics 12.6.2.1 Kinematic viscosity 12.6.2.2 Net calorific value 12.6.2.3 Cetane number 12.6.2.4 Density 12.6.2.5 Flashpoint
296 297 297 297 297 297 297 297 297 297 298 298
12.7 Alternate fuels in compression ignition engines 298 12.7.1 Application of unmodified vegetable oils in diesel engine 298 12.7.1.1 Use of neat vegetable oils in diesel engine 298 12.7.1.2 Use of neat vegetable oil blends in diesel engine 298 12.7.2 Use of biodiesel and its blends 299
Advanced Biofuels https://doi.org/10.1016/B978-0-08-102791-2.00012-X
301 301 301 302 302 302
12.9 Experimental methodology 303 12.9.1 Solvent-assisted oil extraction 303 12.9.2 Biodiesel synthesis 303 12.9.2.1 Esterification 303 12.9.2.2 Design of experiments 304 12.9.2.3 Transesterification 304 12.9.2.4 Biodiesel optimization 304 12.9.2.5 Evaluation of the model and analysis for a variance for biodiesel 304 12.9.2.6 Experimental procedure for kinetics study 305 12.10 Results and discussion 12.10.1 Comparision of predicted yield and actual yield 12.10.2 Effect of process parameters on biodiesel yield 12.10.3 Biodiesel analysis 12.10.4 Gas chromatography/mass spectrometer 12.10.5 Physical and chemical properties of biodiesel 12.10.6 Experimental procedure for engine study 12.10.6.1 Brake thermal efficiency
291
309 309 309 314 315 315 315 318
Copyright © 2019 Elsevier Ltd. All rights reserved.
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12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
12.10.6.2 Brake-specific energy consumption (BSEC) 12.10.6.3 Heat release rate 12.10.6.4 Ignition delay 12.10.6.5 Cylinder gas peak pressure 12.10.6.6 Combustion duration 12.10.6.7 Exhaust gas temperature 12.10.6.8 Carbon monoxide 12.10.6.9 Carbon dioxide 12.10.6.10 Nitric oxide
318 319 319 320 320 321 321 322 322
12.1 INTRODUCTION In the current situation the demand for petroleum has increased due to globalization and industrialization. Engineers, researchers, and scientists are trying to find alternative sources due to the rapid rise in fossil fuel prices and its limited availability. Recently, developing countries like India and China are facing an exponential increase in energy need [1]. In contrast, some of the world’s biggest producers of oil are experiencing political instabilitydue to wars. The global demand for oil will grow from 98 M barrels per day in 2015 to 118 M barrels in a day in 2030. Hence, to meet the predicted increase in oil demand, total petroleum supply in 2030 will have to increase 98 M barrels in a day in 2015 to 118 M barrels per day in 2030. Members of OPEC are expected to provide 14.6 M barrels per day of the increase. Right now, petroleum use in the world is 98 M barrels of oil in a day [2,3]. Diminishing fossil fuel resources have fueled research interest in alternative energy sources. The resources for this renewable energy should be naturally replenished such as wind, hydro, and solar, geothermal, biomass. In that biomass is one of the primary and promising alternatives from this renewable energy sources. Biomass is the biological material obtained from live organisms. Biomass could be transformed into different usable forms of transportation fuels like biogas, ethanol, and biodiesel. The biodiesel is generally derived from edible and inedible biomass sources. The biodiesel obtained from edible oil is not economically viable, since it is depleting of food-grade additives and may cause a negative impact on the world [4,5]. The first diesel engine was invented by using peanut vegetable oil as the working fluid. This thought and research led an idea to go for biodiesel which could be prepared from edible and inedible oils. The importance of inedible oil resources is getting attention throughout the world. The reasons for that are readily available in most of the world, particularly wastelands that are unsuitable for cultivating food crops, remove struggle for
12.10.6.11 Unburned hydrocarbons 12.10.6.12 Filter smoke number
322 323
12.11 Conclusions
323
Nomenclature
323
Acknowledgments
324
References
324
Further reading
327
food, produce valuable byproducts more efficient, more environmentally friendly, and they are more economic related to edible oils. Biodiesel is a promising ecofriendly alternative to fossil fuel. Many renewable sources, including recycled or used oil like waste oil, can be utilized as feedstock. The significance of biodiesel is its ability to be used as a replacement for petroleumbased diesel. Even though the biodiesel production can only take the place of a slight percent of the country’s fuel source, the petroleum market has a proclivity to be easily affected by the alterations in supply [6,7]. Sulfur is one of the critical pollutants present in diesel fuel. High sulfur content in the fuel causes low-level pollution such as smog and affects the environment severely. Diesel fuel sulfur amount falls within the range of 300e500 ppm and has not been managed till lately. Taking away sulfur content from the diesel enormously reduces the lubricity of fuels. Engine efficiency decreases significantly with the reduction of sulfur content, and for improving the lubricities, additives are added to the fuels and lubricating oil. It has been determined that blending ultralow sulfur diesel with biodiesel improves the lubricity which was lost. So, the use of additives to recover lubricity and the additional device to regulate diesel particulate emissions can be avoided using biodiesel [8]. In an effort to decrease reliance on foreign oil, the United States Federal Government has been supportive of growth in the biodiesel industry. Commonly, biodiesel is a mono-alkyl ester which can be synthesized from vegetable oils or animal fats [9,10]. Chemically, biodiesel can be expressed as the mixture of fatty acid alkyl esters (FAAEs). Generally, fatty acid ethyl esters or fatty acid methyl esters (FAEEs and FAMEs) are obtained by the alcoholysis of triacylglycerols (TAGs) from animal fat and vegetable oils with ethanol or methanol. Alkyl esters are formed when triglycerides are reacting with alcohol with the aid of a catalyst. Catalysts which may be either acid or base depending on the process followed in alcoholysis can be homogeneous (single phase) or heterogeneous (more than one phase), and the
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12.2 SELECTION OF FEEDSTOCK
enzyme-catalyzed alcoholysis uses lipases as catalysts. Generally, alcoholysis can be done without the catalyst in which reactions occur at elevated temperatures and pressures. This noncatalyzed alcoholysis still does not have any practical application [11]. Transesterification process was first proposed by Patrick Duffy in the year 1853. In 1893, the earliest diesel engine was invented by Rudolf Diesel and the fuel which was used in the engine was biodiesel produced from peanut. In earlier 1920s and 1930s and later during the Second World War, most countries focused on utilizing vegetable oils as an alternative fuel for CI engine applications. Biodiesel is chemically defined as mono-alkyl ester according to the National Biodiesel Board (USA). Ahmad et al. [10] showed that the liquid-esterebased oxygenated fuel was identical to the petroleum-based diesel fuel but was formed from bioproducts, either animal fats or plant oils. Although biodiesel has many advantages when compared to petroleum-based diesel, the important barrier to its commercial use is the high price for its production. Generally, the cost of feedstock alone consumes 70%e95% of the total biodiesel production cost. Many such alternative fuels have been identified and tested successfully in the past in the diesel engines with and without engine modifications. As each alternative fuel, suggested by researchers has one or a few undesirable characteristics, this prevents the complete substitution of alternative fuels in the place of the existing one. However, still, the search is on to find out the best alternative fuel for the existing diesel fuel. The researchers have adopted the various admission techniques to apply a more substantial fraction of alternative fuels in the existing engines. Many researchers have proved that the identified alternative fuels are partial substitutes for the existing fuels due to their undesirable characteristics [12]. Among alternative fuels, biodiesel has been identified as a versatile fuel to be used in a diesel engine. The methyl esters produced from vegetable oils are unable to compete with diesel fuel due to its cost [13]. Moreover, enough quantity of oils is not produced in the nation to meet its cooking needs. Hence Planning Commission Committee on Development of Biofuel, in its report in the year 2004, noted that inedible oilseeds have to be used for the production of biodiesel. It also suggested that 20% blending of biodiesel with a conventional diesel could save over 13 billion tons of petroleumderived diesel. It is estimated that for every ton of biodiesel production, two tons of oil cakes are produced. Oil cakes are obtained as the residues after the oil is extracted from the seeds. Oil cakes are classified as edible and inedible. Edible oil cakes have substantial protein content with proper nutrients. The composition of oil cakes changes due to local conditions, variety, and extraction procedures. Edible oil cakes are fed to
293
animals. Inedible oil cakes are used as fertilizers. Various research works have been focused on oil cakes to produce industrial bioproducts and other valueadded chemicals. The oil cakes possess good energy content, and their enormous availability can make biodiesel more cost-effective. Hence oil cakes can be exploited to produce biofuels [14]. Hence focus was on utilizing oil cakes, biomass which is available in plenty, but also cheap to be utilized for biofuel production.
12.2 SELECTION OF FEEDSTOCK The inedible feedstocks are naturally available abundantly in a particular region. In Europe, sunflower and rapeseeds are used, and in USA soya been and animal fats are used. Conversion of oil into biodiesel has been initiated by many researchers all over the world. Numerous feedstocks have been investigated for their suitability and compatibility of internal combustion engines. The consensus of oil research works is the reliance on the transesterification of oil using suitable alcohol under certain conditions of pressure and temperature. Recently research work is further focused on the optimization method to get maximum yield. Nye and Southwell [15] have synthesized the rapeseed methyl ester with an optimized condition of 1:6 ratio of oil methanol and 1 wt% of NaOH catalyst concentration. Cvengros and Povazanec [16] experimented the two-step transesterification process of cold-pressed rapeseed oil with methanol at 70 C. The performance of neat rapeseed oil methyl eater (RME) and 5%, 10%, 20%, and 35% blends of RME with diesel was reported by Labeckas and Slavinskas [17]. The maximum torque and power of 273.5 and 281 g/kWh were obtained for rapeseed methyl ester which is 18.7% and 23.2% higher than diesel, respectively. The maximum brake thermal efficiency in the range of 36%e40% was obtained for rapeseed methyl ester which is comparable to diesel fuel. The production of biodiesel from Moringa oleiferawas reported by Rashid et al. [18], using a two-step transesterification method. Viscosity, cetane number, cloud point, pour point, oxidative stability, and lubricity were determined in that study. The viscosity, oxidative stability, cetane number were reported as 4.83 mm2/s at 40 C, 3.61 h, and 67, respectively. The alkaline catalytic transesterification of the M. oleifera oil and an optimum biodiesel yield of 82% were reported. Kufuku and Mbarawa, after optimization of the process parameters such as 1 wt% catalyst, 30 wt% methanol, and 60 C reaction temperature[19]. Production of Moringa stenopetala methyl ester was conducted with ethanol, methanol, and a 1:1 ratio of ethanol and methanol with 1:6 ratio of oil to alcohol.
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The physicochemical properties of the Moringa esters were estimated to assess its desirability to utilize in standard diesel engines. The physicochemical characteristics of the ester mixture of M. stenopetala oil were better than that of methyl ester. Sesame seed oil was obtained in 58 w/w%, by traditional solvent extraction, and this oil has good yield when compared with all other seeds. The transesterification of sesame oil (Sesamum indicum L.) carried out to produce methyl ester with a molar ratio as 6:1, using 1.5 g NaOH as a catalyst, was reported by Saydut et al. [20]. The maximum pomace methyl ester yield was achieved with NaOH catalyst and 1:8 ratio of oil to methanol at 60 C temperature for 1 h reaction time. The study also reported the use of synthetic manganese additives to improve fuel properties [21]. A maximum Croton megalocarpus biodiesel yield of 95% was obtained using SiO2 as a superacid solid catalyst. Free fatty acid value of C. megalocarpus oil is found to be too high compared to other feedstocks, so single-step transesterification could not be possibly reported by Kafuku and Mbarawa [19]. The physicochemical properties such as density, viscosity, flash point, pour point and cetane index, and calorific value of biodiesel produced from Mesuaferrea and Pongamia pinnata were assessed. M.ferrea biodiesel is found to be superior to P. pinnata biodiesel reported by De and Bhattacharyya [22]. The transesterification of P. pinnata oil expelled from the seeds was reported by Sharma et al. [23]. Both alkaliand acid esterification were eventually carried out to obtain the final product. Regarding yield, sodium hydroxide was found to be a more acceptable catalyst than potassium hydroxide. Maximum methyl ester yield of 89.5% was attained with oil to methanol ratio of 1:8 and 1:9 for acidcatalyzed transesterification and base-catalyzed esterification, respectively. The physicochemical properties of oil and methyl ester were determined to satisfy ASTM D6751 standard and utilize the biodiesel in an unmodified diesel engine. Jain and Sharma [24] conducted the kinetic study of Jatropha curcas oil (JCO) with esterification (H2SO4) and followed by the base (NaOH)-catalyzed transesterification. They were conducted at an optimum operating temperature of 50 C and 65 C for transesterification and esterification, respectively. The process was carried out with the most favorable oil to methanol ratio of 7:3 (v/v) and 1% of catalyst concentration (w/w) for both H2SO4 and NaOH. The maximum yield of 90.1% during transesterification and about 21.2% of methyl ester during esterification of pretreated JCO were attained. Performance analysis of neat biodiesel synthesized from karanja, jatropha, polanga, and their blends (B20 and B50) at a different speed in a three-cylinder tractor engine at full and part throttle operations was made
by Sahoo et al. [25]. BSFC for all the biodiesel blends was higher compared to neat diesel operation. The engine power increases with increasing the jatropha biodiesel concentration, and maximum power is obtained for B50 at the rated speed of 2200 rpm. The effect of using linseed oil methyl ester having high linolenic acid in diesel engine was investigated by Puhan et al. [26]. The biodiesel shows the lower brake thermal efficiency compared to diesel due to higher oxides of nitrogen in a constant speed compression ignition engine has a capacity of 4.4 kW. In comparison to the conventional process, the energy requirement of 41.5% could be saved from the proposed biodiesel process. The catalyst is generally used to increase the rate of reaction for the chemical process which was started by Ma and Hanna [27]. In general, there are two types of catalyst involved in this chemical process. One is a homogeneous catalyst in which only one phase component and the other is heterogeneous which involves two or more than two phases. Homogenous catalyst provides fast reaction rate compared to the heterogeneous catalyst, but it is difficult to separate from the reaction mixture. Catalytic reaction of heterogeneous catalyst involves multiple phases. Generally, the catalyst is in the solid phase and the reactant and product are in the liquid phase or gaseous phase.
12.3 OIL EXTRACTION This study reviews the use of vegetable oil, produced on a small scale, as fuel. These are also called straight vegetable oils (SVOs), since they are filtered manually on a small-scale contrary to the advanced refining processes followed by the industries. SVOs are manufactured using simple technology, unlike the industrially manufactured oils. The chemical composition of SVOs differs from the industrially manufactured oils by the fact that SVOs have other minor compounds, for example, phospholipids, waxes, etc., which are present in little quantities or not at all present in the latter. SVOsare composed of 95% of triglycerides and 5% of free fatty acids and various impurities [28e31]. Extraction of oil from seeds involves several techniques like mechanical crushing, solvent extraction, cold pressing, microwave, etc., and extraction of oil from the seeds can be done through five different processes. Water-assisted, manual pressing, expelling, Ghanis, and solvent extraction are those five techniques generally used for the extraction of oil from the seeds [32]. In the waterassisted technique, there are two ways to extract the oil. In the first method, the finely ground oilseeds are mixed with water and heated to the boiling point of water; after a certain period, the oil that floats on the surface is skimmed off. In another method, powdered seeds are
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12.4 TRANSESTERIFICATION
mixed with water and squeezed to release the oil. Manual pressing is one of the general techniques which can be observed in our daily life. In the manual pressing technique, oilseeds are usually preground and are pressed in screw presses manually [33]. Expelling oil extraction technique consists of an expeller which is turning in a perforated cage with the help of an electric motor driven screw. The screw forces the material through a small outlet called as “choke.” High pressure is applied on the oilseed fed through the machine to haul out the oil. Expelling is a continuous method to extract oil continuously unlike manual pressing and water-assisted oil extraction which are batch systems. Ghani is the conventional way of extracting oil from seeds and still widely used in rural areas. In this, dried seeds are feed into the mortar, and it is crushed by rotating the mortar which is either powered by an animal or an electrical motor. The limitations of this method are the extracted oil requires further purification and yield is low compared to modern techniques. Solvent extraction is the widely accepted efficient method to extract oil on an industrial scale. In solvent extraction, oil is mixed with seed powder in a specific ratio, and the mixture is heated to the boiling point of the solvent. Finally, the pure oil is separated from the solvent-oil mixture by distilling the solvent in a rotary evaporator [34,35]. Mahua seeds are partially miscible in water, so it is difficult to extract oil through water-assisted technique, and manual pressing technique also yields less amount of oil per day. So, these two extraction techniques are inefficient and require a large amount of manpower to extract the oil from the seed. Weiss [36] used the cold method of extraction to extract castor oil by the standard method whereas Muzenda et al. [37] used the hot method of extraction to extract castor oil in a laboratory scale. Various extract methods are available for obtaining oil from seeds which are mechanical press, supercritical fluid extraction, and solvent extraction method. The mechanical method of extraction is the most widely used to extract oil from the seed. The turbidity of the oil produced with this method is usually high; it also contains a substantial amount of water and metal contents. Extraction using supercritical fluid generated very high purity oil but having a very high operating and investment cost is a disadvantage [38]. Solvent extraction is the best method to extract oil from seeds, which involves less cost and also gives more yield compared to other extraction techniques. Solvent extraction technique is that type of extraction technique in which seeds are crushed to a specified size for getting better yield and mixed with a solvent which can be separated by distillation [38]. A solution consists of solvent and solute which are chemically different (may be solid, liquid, or gas) in which solute gets dissolved
Storage
Cleaning
Milling, grinding
Oil expelling
Crude oil
Cake
Filtering
FIGURE 12.1
Outline of expelling extraction process.
in the solvent. Generally, solvents are liquids, but it can be in the gaseous state also. The amount of solute which is dissolved in a specific quantity of solvent varies with temperature. Water is considered as the universal solvent for polar molecules; complete proteins and ions are dissolved in water solvent in a cell. There are various applications for the use of a solvent such as in oil, gas, pharmaceutical and chemical industries, including in chemical syntheses and purification processes. Solvent extraction is a highly efficient technique whereas only economical at a larger scale. Usage of inflammable solvents results in the risk of safety and health issues. By considering all these factors and due to less complicity and for extracting more percentage of oil from the seeds generally researchers prefer expelling technique. Fresh seeds of mahua are collected, and then the plant materials are dried in the sun. Then the seeds are subjected to screw impeller mechanical press to extract the oil. Then the collected oil was filtered to remove the impurities and followed by water wash using distilled water. Then the pure oil was collected and then followed by raw oil characterization. The necessary steps involved in processing oilseeds by expeller are shown in Fig. 12.1.
12.4 TRANSESTERIFICATION Transesterification is the well-known chemical method to convert the triglycerides into methyl esters
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[39]. The oil extracted from vegetable source or animal fats are not suitable to unmodified diesel engine due to its high viscosity and acid value. These issues can be overcome by converting it into methyl esters which have similar fuel properties of diesel fuel [38]. Moreover, the cetane number of transesterified vegetable oil is quietly higher than diesel fuel which improves ignition quality of biodiesel in the engine. Catalyst
Triglycerides þ alcohol 5 Methylester þ Glycerol Meher et al. [40] stated that the best way to reduce the viscosity of the vegetable oil is to separate the glycerol molecules from three fatty acids. Mustafa Balat and Hawa Balat [41] gave an exhaustive review of biodiesel as a vehicular fuel. They gave a brief view about transesterification using different catalysts like alkali-based, acid and base catalysts, enzyme catalysts, and noncatalytic transesterification process for biodiesel production using different feedstocks. They also gave a review of the effect of reaction parameters like free fatty acid and moisture, molar ratio, alcohol type, reaction time and temperature, and catalyst on the reaction.
where A is the Arrhenius constant, R represents the universal gas constant (8.314 J/mol-K), T is the reaction temperature in K, Ea is the activation energy, and k stands for the rate constant. In this, the amount of catalyst used for transesterification process is assumed to be sufficient to move the reaction forward to produce the methyl esters, and reverse reaction is not taken into account. Moreover, catalyst concentration changes during the reverse reaction are assumed to be negligible. The second order kinetic model is given in Eq. (12.2). rA ¼
d½TG ¼ k1 ½TG ½ROH3 dt
where TG is the concentration of triglycerides, k1 is the rate constant, and ROH is the methanol. According to this Eq. (12.2), transesterification reaction follows the second-order kinetic model. However, the change in methanol concentration is constant due to high methanol to oil ratio for the reaction. Therefore, considering this excess amount of methanol, the overall transesterification reaction will tend to follow the first-order kinetic model as given in Eq. (12.3), rA ¼
12.5 CHEMICAL KINETICS OF BIODIESEL PRODUCTION FROM INEDIBLE SEEDS Temperature plays a vital role in the transesterification reaction. Hence, the chemical kinetic study is necessary to understand the influence of temperature on biodiesel conversion time [42]. The kinetic study was done to find the activation energy needed for the transesterification process. The minimum amount of energy required to shift the reaction toward the formation of products is known as activation energy which can be estimated from the relation between rate constant and reaction temperature [43]. The minimum energy required to start the product formation can be calculated from Arrhenius equation (12.1). The activation energy, Ea, is estimated from the slope of a plot between ln(k) and 1/T [44,45]. Currently, researchers absorbed the significance of chemical kinetics to estimate the specific activation energy for converting TG into biodiesel. Kinetics study on any reaction will generally provide information to find conversion percentage at a definite interval of time, the rate of conversion, and activation energy (Ea) for the reaction. The rate of methyl ester formation can be estimated by calculating the rate at which methyl ester is formed. k ¼ Ae
Ea RT
(12.1)
(12.2)
d½TG ¼ k1 ½TG dt
(12.3)
The initial boundary conditions for the transesterification reaction assumed as triglycerides concentration is zero at time t ¼ 0, and when the time reaches t it starts to decrease. Finally, the integration of Eq. (12.3) gives Eq. (12.4). ln½TG0 ln½TGt ¼ k t
(12.4)
½TG ¼ ln½TG0 ð1 XFAME Þ
(12.5)
Finally, integration rated form of conversion of methyl ester is obtained from Eq. (12.5) and given as Eq. (12.6) [46]. lnð1 XFAME Þ ¼ k t
(12.6)
12.6 PHYSICOCHEMICAL PROPERTIES OF SVOS The straight vegetable oil obtained from different feedstocks are having different physical and chemical properties. Hence, it is necessary to evaluate the physical and chemical properties of SVOs as per ASTM D6751 and EN14214 before utilizing it in a conventional diesel engine. SVOs quality mainly relies on its parent feedstock, time of harvest, storage conditions, and extraction methods [47].
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
12.6 PHYSICOCHEMICAL PROPERTIES OF SVOS
12.6.1 Chemical characterization 12.6.1.1 Fatty acids The tendency of the fuel to burn appropriately is determined by the fatty acids present, whereas the combustibility of the fuel is determined by the degree of unsaturation of the fuel, which corresponds to the double and triple bonds present in the fatty acids. This degree of unsaturation of the fuel is proportional to the iodine value of the fuel, which is nothing but the number of milligrams of iodine consumed by 100 g of fat or oil. Fuel with low iodine value, that is, more saturated, is ideal for combustion. However, it should be noted that a very low iodine value is also not desired as it can lead to cold characteristics of the fuel. The classification of biodiesel is given in Table 12.1 [29]. The quality of combustion varies inversely with unsaturation, with the saturated fuels offering the highest quality of combustion. The presence of fatty acids in unsaturated oils can cause polymerization which can easily clog the rack actuator of the fuel injection system. On the opposite hand, saturated oils depict a higher viscosity at higher temperatures than their unsaturated counterparts [48]. 12.6.1.2 Phospholipid content During the mechanical oil extraction, there is a chance of phospholipids also being extracted from cellmembrane of seeds and kernel. The percentage of phospholipid varies with pressing force and filtration process. These lipids are undesirable content which are responsible for deposition of gums in the fuel tank and cause fouling in the valves and cylinder chamber. The concentration of phospholipids is getting reduced when seeds are cold-pressed at 50 C [49e51]. 12.6.1.3 Waxcontent Waxes are long-chain fatty acid esters and alcohols that can contain up to 46 carbon atoms. They originate from the shell and skin of specific seeds and fruit, respectively. The fraction of wax will vary depending upon the source of the seed, its ripeness, and the temperature at which oil is extracted. Waxes dissolve in the fuel at higher temperatures and hence should be filtered. During the combustion process, they do not hinder but TABLE 12.1
Classification of SVOs based on their iodine values.
Name
Iodine value
Examples
Saturated
5e50
Copra, palm-kernel oils
Monounsaturated
50e100
Groundnut, rapeseed, olive
Di-unsaturated
100e150
Sunflower, soybean, corn
Tri-unsaturated
>150
Flax, tung
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can cause blocking problems in the feed circuit, pump, and filter due to their high viscosity [51]. 12.6.1.4 Peroxide value This is used to determine the stability of the oil by evaluating its oxidation value. As it is obvious, the more the fuel is unsaturated, the more it is vulnerable to oxidation. Unsaturated fatty acids undergo fission, by splitting at the multiple bonds to give a series of short-chain compounds such as aldehydes and ketones which manifest themselves in the rancid odor of oils and fats. The rate of the reaction is slow initially but then increases exponentially. Van Grepen [52] showed that there exists a range of peroxide values for which cetane number increases linearly with the peroxide value.
12.6.2 Physical characteristics 12.6.2.1 Kinematic viscosity The viscosity of the neat vegetable oil is higher than that of the diesel fuels by 10e15 times at ambient temperature [53]. Viscosity is also observed to increase with increase in carbon chain lengths and unsaturation and decrease with rise in temperature. Viscosity can also be attributed to the high molar masses of the oils. The high viscosity of biodiesel decreases the injection flow which significantly reduces the pressure in the injection pump, filters, injectors, nozzles prompting poor atomization and vaporization. This issue makes the combustion incomplete [30,54,55]. Apart from that, viscosity dramatically affects the lubrication property. Some of the recent techniques to get over the difficulties faced by high viscosity are preheating, dual-fuelling, and mixing [51]. 12.6.2.2 Net calorific value This determines the heat given off per kg of combustion of the fuel. Although the value of absolute net calorific value (NCV) of SVOs is lower than that of diesel by 10%e15%, considering the high density of vegetable oils, the volumetric NCV of the SVOs is less than that of diesel fuels by 5%e6%. Forgiven unit power produced, this means 8% extra consumption of vegetable oil. NCV and density are the two parameters used to measure the volume flow rate of SVOs over diesel to inject the same power [51]. 12.6.2.3 Cetane number This signifies the time between the injection of the fuel and the start of its combustion. The higher cetane number of fuel indicates that the fuel is more flammable. The cetane numbers for vegetable oils are lower (29e43) than diesel (45e55). This produces difficulties in coldstarting and increased noise. At present, very few
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standard methods are only available to determine the vegetable oil and its biodiesel cetane number. Hence, there is a need to develop satisfactory analysis techniques to determine the viscosity of SVOs correctly [51]. 12.6.2.4 Density The density of SVOs is around 10% higher than the diesel fuels, and as mentioned above is a parameter used to determine the flow rates [51]. 12.6.2.5 Flashpoint Flashpoint is the minimum temperature at which the vapors from the oil get ignited when they are exposed to an external flame. In case of fuels, this acts as a safety parameter that determines its storage properties. The flash point of SVO is significantly higher than that of the diesel. Hence for these reasons, storage of diesel fuels needs extra precautions [51].
12.7 ALTERNATE FUELS IN COMPRESSION IGNITION ENGINES The compression ignition (CI) engine is currently the most efficient engine used for power generation and transportation. Also, its flexibility for different fuel and their blends makes it the most important type of engine for both automotive and power generation industries. Despite all these features of CI engine emission of greenhouse gases (GHG), NOx and particulate matter are the primary key factors leading to the search of new and more efficient ways to diminish emissions [56]. Many alternative fuels have given successful outcomes in the past, with both modified and nonmodified diesel engines [57]. The presence of certain unacceptable characteristics in the alternative fuels hinders its complete replacement of diesel fuels. Researchers have improvised upon the different admission techniques to maximize the fraction of alternative fuel that can substitute diesel [58]. Biodiesel consists of fatty acids and alkyl esters which can easily be used in compression ignition engine [59,60]. Its biodegradable and nontoxic nature derived from its biological origins make it even more attention-seeking [61]. It can also be termed as a cleaner fuel because of the absence of carcinogenic agents. Vast research has proved biodiesel to be an effective alternative to petrodiesel [62].
12.7.1 Application of unmodified vegetable oils in diesel engine 12.7.1.1 Use of neat vegetable oils in diesel engine A previous durability test on a diesel engine with mustard oil indicated that output power was decreased
as compared to diesel. Also, for mustard oil, CO emissions were higher at lower loads [63,64]. Coconut oil mixed with diesel in indirect injection diesel engine delivered higher brake power and net heat release rate, and diminished the amount of pollutants being discharged [65]. Long-term engine tests of palm oils and diesel mixes on a cutting-edge coordinate, direct injection diesel engine were performed. It was reported that the performance of engine smoke intensity and fuel consumption were found to vary marginally with running time [66]. Vegetable oils were used to run diesel engines directly, and some vegetable oils like karanja oil, rice bran oil, cottonseed oil, sunflower oil, jatropha oil, palm oil, etc., have been tested as fuels in diesel engines [67]. The literature review has indicated that, for short duration period, neat vegetable oils can give satisfactory performance in unmodified diesel engines. Also, it has been revealed that the complete substitution of vegetable oils has resulted in a slight decrease in maximum engine power and increase in fuel consumption compared to diesel fuel. A disadvantage of vegetable oils is its high viscosity resulting in poor atomization causing incomplete combustion [68]. This results in engine fouling due to carbon deposit on the injector and the valve seats. Another issue ruining routine utilization of common vegetable oils in present-day diesel engine is high sensitive viscosity, because of glycerine, which convolutes distribution (driving), sifting, and predominantly the exceptional atomization of the saturated fuel [69]. Vegetable oils are introduced as fuel for their substantial performance (emissions, efficiency, etc.), yet also to a specific number of issues experienced in their utilization. Such issues are often represented in writing: combustion chamber deposits, blocked filters, and various kinds of preparations are recommended: - mixing of vegetable oils in different percentages with diesel, - dual-fuelling or preheating vegetable oils, - employing exhaust gas recirculation (EGR), - combustion chamber modifications (injector, piston, etc.). The essential factor many times being emphasized via publications is that if vegetable oils are to be used efficaciously in a diesel engine, it is vital to have oil of good quality and also to make the integral adjustments to the engine [30,53]. 12.7.1.2 Use of neat vegetable oil blends in diesel engine Durability tests were conducted on direct injection, naturally aspirated, ford tractor three-cylinder diesel engine with sunflower oil and soybean oil. It was found
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that various amounts of vegetable oil with diesel fuel and different conditions of operation could provide different results on emissions and performance [70]. Research has also been done on the consequences of employing diesel-coconut oil blends and pure coconut oil on the emissions and performance of a diesel engine with direct injection. Increasing the quantity of coconut oil in the coconut oil-diesel blends hasresulted in lower smoke and NOx emissions. They also reported that the fuel consumption (BSFC) was increased due to the lower calorific value of neat coconut oil fuel compared to diesel fuel. The spray pattern of coconut oil and the blend with diesel was also analyzed at different temperatures and that due to the lower calorific value of coconut oil, the heat release patterns showed lower spikes with reduced premixed combustion [71]. Experiments on a DI-CI engine using degummed Jatropha curcas oil (with an objective of avoiding many problems such as injector coking, high exhaust gas emission, and effect to the engine components) were conducted and combustion and emission characteristics of CI engine were reported. It was reported that 10% degummed J. curcas oil (DJO10) blend gives better combustion compared to 10% J. curcas oil (JO10) and the efficiency of both fuels were closer to diesel. It was also reported that HC, CO of JO10, DJO10 are higher than diesel fuel. NOx emission of JO10 is increased by 9.38% and for DJO10 decreased by 0.44% compared to diesel fuel. Smoke emission is reported to be less [72]. The performance of vegetable oils in a four-stroke, single-cylinder, stationary diesel engine was examined. The linseed oil, mahua oil, rice bran oil, and ester of linseed oil were blended with diesel at different proportions and tests were conducted. It is reported that the performance of vegetable oils is near to that of diesel and could be used for agricultural purposes [73]. Experimental investigation on a direct injection CI engine at constant speed and evaluated performance, emission, and combustion behavior of blended jatrophaoil under unheated environments were performed. It was concluded from the results that jatropha blends 20% or less were found to be promising alternative fuels. They could be directly used in CI engines without any major modifications in the engine [74]. The difficulty of low volatility, polyunsaturated characters, and high viscosity can be altered by blending of diesel with vegetable oils and henceforth resolve the difficulties of operation of the diesel engine with pure vegetable oil [75]. It is noticed that without any modification a diesel engine would successfully run on a blend of 80% diesel with 20% of vegetable oil without any damage to the parts of the engine. Refined pure vegetable oils cannot be directly used in diesel engines with directinjection [76],when such engines bring up to half of their theoretical power and have a mean chamber
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temperature less than 200 C. Though, the flash point of vegetable oil is more than diesel oil: 93 C for diesel oil as contrasting to 240 C for jatropha oil. It means that few of the oildroplets will not be evaporated; instead they will stick to the walls, ensuing in deposits of tar. Shortly after such deposits accumulate on the nose of the injector, there will be trouble in spraying and then the operation worsens. Also, they enter in top ring of the piston throat, restraining workability and result in clogging and quick wear of the ring [51]. Direct-injection diesel engines are most widely used to generate shaft power and current, and in rural applications, it appears more appropriate to examine their operation with SVO as a fuel. Still, such engines create complications when vegetable oil is employed.
12.7.2 Use of biodiesel and its blends The performance, emissions, and combustion characteristics of a diesel engine fuelled with biodiesel, without any engine modification, were carried out by a different researcher. It was found that at maximum load conditions the specific fuel consumption of biodiesel is more by 17% that of diesel. The brake thermal efficiency with diesel is 25.9% and decreased to 24.5% with biodiesel [77]. Overall combustion characteristics of biodiesel and its blends are found to be quite similar to diesel. Brake-specific fuel consumption (BSFC) is the ratio of the mass of fuel consumed by the brake effective power generated in an engine. BSFC is inversely related to thermal efficiency. Increase in BSFC is accredited to enhancement of oxygen from the fuel and not from the intake of air. Almost all investigators have described an increase in BSFC when using biodiesel blends and biodiesel. When using biodiesel, most of the scientists have seen a substantial variation in thermal efficiency [78,79]. Torque, brake power, SFC, and brake thermal efficiency were found comparable to that of the dieselfuelled engine when esterified palm oil was used as a fuel for CI engine [80]. The calorific value of petroleum diesel is approximately 5% more than the calorific value of cottonseed oil (CSO) biodiesel. The torque and power was hence reduced because of lesser calorific value [81]. The experiment was carried out by Pongamia glabra, rice bran oil, palm oil, rapeseed oil, and neem oil for an alternate fuel for diesel engine. The results of the tests were discussed concerning the performance and combustion parameters like delay period. These results indicated that the vegetable oils and their methyl esters performed with acceptable thermal efficiencies as fuels for diesel engines. Methyl esters of vegetable oils had shorter ignition delays and longer combustion duration than diesel oil due to their higher viscosity [82]. The atomization of fuel was affected by higher viscosity and surface tension of the fuel. The coconut oil methyl ester
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had got the smallest mean drop size when compared to peanut and canola methyl esters due to its lower surface tension. This reduction in fuel drop size improves the combustion efficiency of the fuel. The fuel atomization is affected by surface tension. The biodiesel with higher surface tension offers resistance to fuel atomization [83]. The bulk modulus is an important parameter for the combustion analysis; it is a measure of resistance to compressibility. Bulk modulus decreases with increase in temperature and increases with increase in pressure. The vegetable oil esters are less compressible than diesel. This less compressibility leads to increased mass delivery of the fuel. The high value of bulk modulus causes an advance in injection timing which leads to more fuel accumulation in the combustion chamber. It was reported that the bulk modulus is higher for unsaturated methyl esters and increases with the chain length of the acid [84]. Therefore, a quicker transmission of the pressure wave is received by the nozzle commencing injection pump, hence the elevated needle in advance. It also leads to an earlier injection of biodiesel at elevated pressures and same crank angle in the combustion chamber. The quantity of the fuel at an early stage of premixed combustion rises because of increase in injection pressure [85]. It has been found from most of the research work that biodiesel fueled engines emit more NO than diesel. Generally, NOx formation is influenced by the exhaust gas temperature (EGT). The NOx formation is dependent on the temperature inside the cylinder and the NOx formation reaction requires high activated energy. Higher temperature would convert the atmospheric nitrogen into NOx [86]. The presence of carbon in biodiesel molecule has a biological nature. Each rapeseed oil methyl ester (RME) molecule comprises about 94.73% organic carbons whereas in the case of rapeseed oil ethyl ester (REE) molecules the biological carbon is almost 100%. This biological carbon increases the exhaust gas temperature by about 5 C in the biodiesel blend and this is another reason for the increase in NOx [87]. The viscosity of the fuel is also one of the reasons for NOx formation in CI engine. The fuel viscosity affects the fuel injection characteristics and fuel atomization. The increase in viscosity leads to an increase in biodiesel fuel injection by mass. The disadvantages of having a higher viscosity of biodiesel are as follows: increased spray jet penetration, lower spray cone angles, and bigger droplet sizes also result in poor atomization. Early start of injection along with lower spray cone angles is the primary cause for lesser thermal efficiency and increased NOx emissions of biodiesel [88]. Iodine number is another parameter influencing the NOx formation in CI engine. Biodiesel blends with high iodine number and low iodine number fuels could support reducing and increase in NOx, respectively. The
animal-based biodiesel has a lower iodine number than those for rapeseed- or soy-based biodiesel. Also, lowering the aromatic content in the animal-based biodiesel could help in reducing NOx emission [89]. Organic compounds consisting of a peroxide group bonded to two tert-butyl groups and compounds like ethylhexyl nitrate are cetane improvement additives that may also be helpful for NOx reduction [90]. Increase in unsaturated fatty acid reduced the cetane number and increased the iodine value. The increase in saturated fatty acid content increased higher heating values [91]. The most common fatty esters contained in biodiesel are mainly C12 to C16 fatty acids including lauric acid (C12:0), myristic acid (C14:0), palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2), and linolenic acid (C18:3). Emission tests were conducted in a CI engine and observed that there was a decrease in NOx emissions with saturated fatty acids like lauric acid and palmitic acid and increase in emissions with unsaturated fatty acids like linoleic acid [92]. The formation of smoke happens primarily in the cylinder at fuel-rich zone, high pressure, and low temperature. Formation of smoke can be governed by the availability of oxygen decreases overrich regions (it is the region where the fuel is more than needed, i.e., more than the desired fuel-air ratio) [93]. When the engine runs at full open throttle on underload, all of the fuel is injected to give maximal power, which is a rich mixture. Therefore, at higher load, fuel-air ratio increases, fuel is injected in huge amounts, and most of the fuel which is unburnt escapes with the exhaust ensuing in increased emissions of smoke. Formation of smoke was less under the load condition less than 75%, and it increases with the increase in load [94]. The CO generated in the clean diesel fuel could be reduced by 24% if 30% of biodiesel is blended with it. This is because biodiesel contains higher oxygen content compared to the conventional fuel to enhance the complete combustion [93]. The CO2 released by burning biodiesel would not harm the environment, and it does not contribute to the greenhouse gas formation. The reason behind this is because biodiesel is produced from the crops which use the already available CO2 which is present in the atmosphere. However, in the case of the commercial petroleum diesel, the CO2 released are from the deposited carbon inside the earth’s crust which contributes to the greenhouse gas effects [95]. The maximum thermal efficiency and preferable reduction of engine emission were attained in 20% biodiesel blend. So, it was found to be optimum condition for linseed oil methyl ester (LOME) that improved the thermal efficiency of the engine by 2.5%, reduced the exhaust emissions, and the specific energy consumption was higher; and there was the reduction in exhaust smoke levels. Exhaust temperatures were increased
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due to a higher percentage of LOME which led to a 5% increase in NOx. The experimentation verified that self-lubricity of LOME in biodiesel contributed to engine performance significantly. The additional lubricity provided by B20 demonstrated comparable power and torque as generated by the combustion of commercial petroleum fuels [96].
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Due to stringent emission norms, most automobile manufacturers are downsizing engines and supercharging them to produce the required power and torque, while increasing overall efficiency. Butin the near future it will be required to resort to renewable fuels to run our engines, as fossil fuels are getting depleted. The easiest way to move on is by modifying existing engines to run on renewable fuels [97].
engines. Many authors have investigated the effectiveness of this method and suggest that increasing the intake air pressure is achieved either through turbocharging or supercharging. Al Hinti et al. [102] boost up the suction air pressure could increase air density and improve the volumetric efficiency of engines during each cycle. Generally lower end engine, the suction air pressure was increased in between to 0.2 and 0.8 bar. The output power of engine varies on the value of suction pressure increase and the engine geometrical and operational condition. As mentioned earlier, forced intake has been identified as one of the most promising engine modification to meet increasingly strict emission standards without compromising on the power, performance, and efficiency of the IC engine. This concept could be effectively put to use in making biodiesel a more prominent and promising alternative for diesel in CI engines.
12.7.3.1 Forced intake air pressure The phenomenon of forced intake can be defined as supplying air to the engine at a higher pressure than 1 atmosphere. By doing so, we are forcing air into the cylinder during suction stroke in addition to the sucking action of the air by the engine. This increased pressure will induce some amount of pumping loss in the compression stroke, but the benefits of forced intake outweigh its drawbacks. As per the universal gas law, with an increase in intake pressure for the same swept volume, the mass of air forced into the cylinder increases [98]. This increased intake air mass helps improve combustion and produce cleaner emissions. The cause of the same can be explained by the simple heat transfer law H ¼ mCpDT. Assuming that the coefficient of heat transfer remains constant (almost) for a certain amount of heat, the increased mass will lead to a reduction in DT. Hence, the forced intake pressure method reduces the in-cylinder temperature compared to a naturally aspirated engine by providing the same amount of fuel [99]. As NOx production is a function of temperature, the same is expected to reduce significantly after pressurizing the intake air. Improvement in fuel economy is also expected when forced intake phenomenon is applied [100]. Karabektas [101] studied the effects of a turbocharger on a diesel engine with biodiesel as fuel. BSFC was increased for biodiesel due to lower calorific value and higher density of biodiesel. Smoke emission decreased for turbocharged engine and NOx emission was increased due to better combustion. However overall performance of the turbocharged engine improved when compared to the naturally aspirated engine. Increase in the suction pressure of air is an effective approach to improve the efficiency and power of IC
12.7.3.2 Fuel modification Addition of dimethyl carbonate to mahua oil biodiesel by 5%, 10%, 15%, and 20% reduces the NOx emissions. The increase in additives reduced the NOx emissions by 40% and improves the thermal efficiency by 5%. HC and carbon monoxide emissions reduced marginally with an increase in an additive to mahua oil biodiesel [103]. Blending with another fuel with better cold flow properties is inevitable. More researches are performed by adding alcohol as an additive with biodiesel to improve cold flow properties, and a few types of research involved the oxygenated diethyl ether addition at a lower volume comparatively. Such changes in fuel improved cold flow properties and also resulted in better combustion and reduced emission characteristics. It also includes the blending of diethyl ether with biodiesel which improves the cold flow properties and cetane index [104]. Pyrolytic distillation methods are used for producing diesellike fuel (DLF). During the test, it is observed that the distillation temperature of the DLF was close to a typical diesel fuel sample. Hence, The DLF can be used in CI engine fuel. The DLF has an advantage of increases the engine torque, brake thermal efficiency, brake mean effective pressure, and decreases specific fuel consumption of the engine for the rated loaded condition [105]. Compared to CaO and trisodium phosphate, tripotassium phosphate shows high catalytic action during transesterification reaction [106]. About 97.3% fatty acid methyl ester (FAME) yield wasobtained with a catalyst concentration of 4 wt% at 60 C for 120 min. In addition to this, used regenerated catalyst with aqueous KOH solution for transesterification obtained FAME yield of 88%. Mixing of cosolvent converted the reaction state from three-phase to two-phase but decreased the FAME yield which is exact opposite of
12.7.3 Engine and fuel modification
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homogeneous catalysts. In the presence of cosolvents for reducing the catalytic activity the catalyst particles were agglomerated by the glycerol drops. 12.7.3.3 Engine modification On the basis of earlier research, it was identified that the engines running on the biodiesel emit lower CO, unburned HC, and PM compared to emissions from diesel; it was observed that there was a small rise in NO emissions. Further reduction in emission can be achieved by either use of a modification of engine operating parameters, fuel additives, or after-treatment techniques [107]. Among these methods, after-treatment techniques like diesel particulate filter (DPF) has become more popular as it controls the particulate matter which comprises mainly of carbonaceous soot particles that cause a severe hazardous effect on the environment [108]. The blending of jatropha oil and diesel in the low heat rejection diesel engine (L.H.R) improves the performance compared to raw jatropha operation. Combustion duration and ignition delay also reduces with blending of jatropha oil and diesel. A substantial amount of this waste heat can be recovered by applying a thermal barrier coating (TBC) on the cylinder liner, piston crown, cylinder head, and exhaust valve. It reduces the heat loss due to conduction and keeps the outer surface temperature lower which eliminates the necessity of water circulation for cooling. Also, the average in-cylinder temperature increases which results in combustion of charged particles trapped in the crevices which do not take part in combustion due to low temperature. Thus, improvement in the combustion of fuels leads to higher efficiency [109]. Increasing the jatropha fuel injection pressure from 200 to 240 bar increases the brake thermal efficiency and decreases the smoke emission [110]. Advancement of injection timing is required for blends of biodiesel and ethanol with diesel due to the displacement of 50% diesel by the blends. The results revealed that advancing start of injection led to earlier combustion. Advance injection timing doubled the NOx emissions and reduces the smoke emission by 60%e70% for all the blends. Due to earlier combustion increase in cylinder pressure, temperature, and NOx emission was observed. The carbon monoxide emission reduces with advancing the injection timing significantly at lower loads [111]. Preheating of biodiesel also significantly increases the efficiency and reduces the emissions. But NOx increases due to the presence of unsaturated fatty acids and the advanced injection caused by the higher density of jatropha biodiesel [112,113].
12.8 ENGINE EXHAUST EMISSIONS The diesel engine has become a preferred prime mover among the various kinds of internal combustion
engines because of its higher thermal efficiency and lower fuel consumption. This includes heavy trucks, buses, industrial power generation equipment, offhighway construction, and mining equipment [114]. Emissions from diesel engines including carbon monoxide (CO), carbon dioxide (CO2), nitric oxide (NO),unburned hydrocarbon (HC), sulfur oxide (SOx), nitrogen oxide (NOx), and particulate matter (PM) lead to severe respiratory disorders. Reduction in CO is generally accompanied by an increase in CO2 [115]. Total hydrocarbons are waste fuels which could not be combusted, and so the presence of the same is an indication that engine is not running at full efficiency. Oxides of nitrogen and sulfur are more hazardous in comparison to the emission above products and contribute to depletion of ozone layer. So, stricter emissions standards are being implemented keeping in mind the deteriorating health of Mother Earth [116]. In the past two decades, many types of research have been conducted to control the emissions. Various parameters were taken into account, which included engine design modification, exhaust after treatment,fuel modification, etc. Smith [117] inscribed, “Hence we summarize, as others have done, that formation of soot is essential in the operation of compression ignition engines.” This was the most common opinion at earlier times but later, following experiments have verified that emissions such as soot can be limited in engine cylinder itself, as revealed by Tree et al. [118]. Among the listed methods, after-treatment techniques like diesel particulate filter (DPF) have become more popular as they block the particulate matter which comprises mainly of carbonaceous soot particles that cause a severe hazardous effect on the environment and respiratory system [119].
12.8.1 Formations of emissions The United States Environmental Protection Agency released a technical report regarding nitrogen oxide. NOx specifies a family of seven compounds. Nitrogen dioxide (NO2) is a leading air pollutant, and as well it reacts with the surroundings to form acid rain and ozone (O3). It is significant to know that the ozone that we need to reduce is ozone present in the troposphere; especially, ozone in the atmospheric air that we inhale [120]. The family of NOx compounds and their properties are listed in Table 12.2. NOx emissions from combustion are mainly in the form of NO. According to the Zeldovich equations, NO is produced at temperatures above 1300 C and due to the amount of oxygen available (about 200,000 ppm) in the atmosphere. At temperatures less than 760 C, nitric oxide is either produced in minor concentrations or not even a trace. NO is formed as a function of air to fuel ratio and is further noticeable when the
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TABLE 12.2
Family of NOx compounds and their properties [120].
Formula
Name
Nitrogen valence
N2O
Nitrogen oxide
1
NO N2O2
Nitric oxide 2 Dinitrogen dioxide
Colorless gas, slightly water soluble
N2O3
Dinitrogen trioxide
Black solid, water soluble, decomposes in water
NO2 N2O4
Nitrogen dioxide 4 Dinitrogen tetroxide
Red-brown gas, very soluble in water, decomposes in water
N2O5
Dinitrogen pentoxide
White solid, very soluble in water, decomposes in water
3
5
Properties Colorless gas, water soluble
mixtures are on the lean side of the stoichiometric ratio of 50 [121]. The Zeldovich equations are [120]: N2 þ O /NO þ N
(12.7)
N þ O2 /NO þ O
(12.8)
N þ OH /ON þ H
(12.9)
Emissions of hydrocarbon generated from the existence of partially burned or unburned fuel in the exhaust of the engine. HC emissions are various compounds of hydrogen, carbon, and sometimes oxygen. Emissions of HC result in the formation of ozone, which causes eye irritation and produces photochemical smog. Though, some of the exhaust hydrocarbons are not found in the fuel but are hydrocarbons resulting from the fuel whose composition was altered due to a chemical reaction that did not go to termination. For instance: formaldehyde, 1,3, acetaldehyde, benzene, and butadiene, all are classified as harmful emissions [122]. CO generation is well recognized. The conditions at which there is no sufficient oxygen required for complete oxidation and some of the carbon in the fuel turns out to be CO. The proportion of CO, for C/H ratios and a fuel composition range, is a function of the relative airfuel ratio. Even in a situation in which enough oxygen is present, dissociation can occurby high-peak temperatures. In combustion chemical reactions water vapor and carbon dioxide separate into CO, H2, and O2. The chemical reaction governs the transformation of CO to CO2. CO þ OH 4CO2 þ H
(12.10)
The exhaust gases are passed through the filter to separate particulate matter (PM) which consists of soot and other liquids, as well as solid materials. Generally, the particulate matter is separated into dry fractions or
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a soluble or insoluble fraction. The insoluble fractions are responsible for determining the soot percentage in the exhaust gases after filtration. Often the diesel exhaust consists of an insoluble fraction with approximately half of the soot contents in it. The other half of the insoluble fraction consists of water vapor, unburnt oil or fuel, wear metals and sulfate compounds generated during combustion [123,124]. The advancement of hydrocarbons presents in liquid or vapor phase to get converted into solid soot particles and feasibly again to gas phase products comprise of six different ordinarily known processes which are in the order as follows: pyrolysis, nucleation, coalescence, surface growth, agglomeration, and oxidation. The last process is oxidation where hydrocarbons get converted into CO, CO2, and H2O throughout the process. All the processes mentioned above occur separately may be in different space constraints or time constraints such as in laminar diffusion flames [125].
12.9 EXPERIMENTAL METHODOLOGY 12.9.1 Solvent-assisted oil extraction Mahua seeds were collected from in and around Trichy areas. Collected seeds were dried in sunlight to get rid of moisture and maximize the oil yield. The dried seeds were crushed into a particle size of 1 mm. Oil extraction was carried out in a 500 mL single neck round bottom flask with 1:5 ratio of seed to solvent. The process temperature was maintained at 40 C with the help of water bath. After 1 h of extraction time, the solvent-oil mixture was taken into the rotary evaporator to separate the oil and solvent.
12.9.2 Biodiesel synthesis Free fatty acid value is the deciding factor to produce biodiesel whether by undergoing single or two-step transesterifications. The FFA of mahua oil is found to be 25 mg KOH/g of an oil which is far high than limits. In this condition, it is not advisable to use base catalyst because of soap formation during the transesterification process. Hence, two-step transesterification process was taken to produce biodiesel. In the first step, acid catalyzed transesterification was performed to reduce the FFA to less than 1 mm KOH/g of oil. Then basecatalyzed transesterification was carried out. 12.9.2.1 Esterification The esterification process was performed on a hot plate which is equipped with reflux condenser, magnetic stirrer, and temperature controller. Mahua oil is initially heated at 60 C for an hour to evaporate the moisture.
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After that 1:6 ratio of methanol and 2 wt% of sulfuric acid were added one by one to the oil. Then the esterification was carried out for 30 min on a hot plate with electrical power of 350 W at 55 C. After completion of the esterification process, the mixture is shifted to separating funnel and kept for 2 h to form two distinct layers. In these two layers, top layer consists of excess methanol, impurities catalyst and bottom layer contain esterified Mahua oil. The acid value of esterified Mahua oil is determined by titration method which is found to 0.8 mg KOH/g of oil. 12.9.2.2 Design of experiments Optimization of CH3ONa catalyzed transesterification was performed using the design of experiment tool. For this Design Expert 10.0 software used to design the transesterification experiments. Response Surface Methodology (RSM) method was chosen to optimize the process parameters such as temperature, catalyst concentration, molar ratio, and reaction time and study the effect of these parameters on biodiesel yield. Table 12.3 presents the parameter range and levels of independent variables for biodiesel production. 12.9.2.3 Transesterification The detailed photographic view and the experimental biodiesel setup is shown in Fig. 12.2, and the transesterification processes use a three-neck round-bottomed flask having a capacity of 500 mL batch reactor. Methanol with 99.9% purity was used for transesterification. The apparatus was employed with Remi adjustable speed DC motor, a Liebig condenser, k-type thermocouple with a thermometer pocket, a mechanical kneader along with a tachometer, and a stopper for sample removal. The reaction temperature was maintained with the help of a constant temperature heating mantle with 0.1 C accuracy. The transesterification reaction was performed with methanol to oil ratios (3:1, 6:1, 9:1, 12:1, 16:1), 0.5%, 0.88%, 1.25%, 1.63%, 2% by weight of catalyst and the reaction was carried at temperatures 40, 45, 50, 55, 60 C and the reaction times were 60, 90, 120, 150, and TABLE 12.3
Input parameters for biodiesel production.
180 min, respectively. The esterified oil was preheated for half an hour at 60 C. After the oil reached the desired temperature, the methanol and catalyst were mixed according to the trial condition. After accomplishment of the reaction, the product was allowed to settle in a separating funnel for minimum 24 h. Finally, the glycerol was removed from the bottom of the separating funnel to get mahua biodiesel from the top of the funnel. Then the biodiesel was subjected to water wash. In this process, distilled water is taken such that the quantity of water taken must be more than double the amount of oil. Then the distilled water was heated up to 50 C. Then this warm water and biodiesel are mixed in a flask and stirred thoroughly and kept in a separating flask for 30 min so that the sediments, excess alcohol, and other impurities were separated from the biodiesel. Then the water is removed from the flask, and the remaining oil was heated up to 70 C, to get the biodiesel which was a clear yellow liquid. 12.9.2.4 Biodiesel optimization In this research, studies on optimization of methyl ester yield are carried. The most critical factors affecting the yield of the biodiesel production are molar ratio, catalyst concentration, reaction temperature, reaction time, and stirrer speed. In order to study the combined effects of all the above-discussed parameters, simulation tools (RSM tool in DoE software) are used. The optimized results, that is, trials which are obtained from DoE software are utilized practically for production of biodiesel from inedible source, using methanol (CH3OH) like alcohol, sodium methoxide (CH3ONa) as a catalyst. Design of Experiment (DoE) software has given 32 experiments to optimize the transesterification process. Those trials were conducted, and the maximum yield for biodiesel was found out to be 95.4%. The results have been tabulated for each trial in Table 12.4. Out of the 32 optimal trials conducted for the production of biodiesel, a trial with 1:9 M ratio, 1.25% catalyst, 52.5 C temperature for 120 min and 800 rpm stirrer speed has given the maximum yield. Mass production of biodiesel is now done in this optimized condition. Fig. 12.3 shows biodiesel production process for different trials. 12.9.2.5 Evaluation of the model and analysis for a variance for biodiesel
Range and level Independent variables
L2
L1
0
D1
D2
Temperature ( C)
40
45
50
55
60
Reaction time (min)
60
90
120
150
180
Molar ratio (methanol:oil)
3:1
6:1
9:1
12:1
16:1
Catalyst concentration (wt%)
0.5
0.88
1.25
1.63
2
Stirrer speed (rpm)
600
700
800
900
1000
From the ANOVA results of transesterification process it is evident that the linear terms A, B, C, D; quadratic terms A2, B2, C2, E2; and interaction terms AB, AC, AD, BC, BD, CE, DE are significant terms to affect the biodiesel conversion. The ANOVA response for the transesterification process ispresented in Table 12.5. The principle model analysis was based on the analyzing of variance, which provides the numerical
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1
2
45 5
1
3
6
Water out
2
4 Water in
4 7
3
5 6 8
7 8
1. Temperature controller
5. Stirrer rod
2. Motor
6. Thermocouple
3. Condenser
7. Three neck round bottom (RB) flask
4. Motor Stand
8. Heating mantle
FIGURE 12.2 Schematic and photographic view of transesterification setup.
information for the “P-value.” The statistical analysis of the response parameter (yield of inedible oil-ME) is shown in Table 12.5. It was observed that the model is significant due to “P” value lower than .0001 (reference limit of “P” value was chosen as .05). The regression analysis gave a quadratic model which is given below Yield ¼ 49:35 þ 2:53A 13:77B þ 9:84C 4:67D 0:67E 0:87AB þ 9:50AC þ 4:37AD 3:50AE þ 9:37BC 5:50BD þ 3:88BE þ 0:63CD þ 9:75CE þ 2:87DE þ 1:67A2 þ 4:76B2 5:10C2 þ 1:51D2 þ 3:13E2 (12.11) 2
The goodness of estimation (changeable R ) and the statistical regression fit (determination coefficient-R2) were computed as 0.9247 and 0.975, correspondingly. The changeable R2 value refers to the number of prognosticators in the model, and R2 value specifies the total response variability later considering the significant factor. Together they specify whether the models fit well or not. Adjusted R2 and R2 value postulated that the accessibility of the model and accuracy were fair that roots the response plots study with the model was feasible. Several chemical and physical properties for the biodiesel characterization were determined. The properties consist of density, fire and flash point temperatures, pour and cloud point temperatures, kinematic viscosity, acid value, carbon residue, copper strip corrosion, and calorific value.
12.9.2.6 Experimental procedure for kinetics study Mahua oil was made to react with methanol using the homogeneous catalyst (CH3ONa). The trial condition used is temperature 45, 50, and 55 C, oil to alcohol ratio of 1:9 for 120 min using 1.25 wt% of the catalyst. At a time, the interval of 24, 48, 72, 96, and 120 min, 2 mL of samples were taken out and sent for 1H-NMR spectrum analysis. Methyl ester formed during each time interval is obtained making use of the NMR chart. In NMR spectrum, the formation of methyl ester and excess methanol are indicated at 3.6 and 3.5 ppm, respectively. The unconverted triglycerides that are protons of CH2 groups are present at 2.3 ppm. The percentage of conversion of methyl ester is calculated using following Eq. (12.12). C ¼ 100
ð2 XÞ ð3 YÞ
(12.12)
where C ¼ Conversion of triglyceride to methyl ester, X ¼ Integration value of the protons of the methyl esters from NMR chart Y ¼ Integration value of the methylene protons NMR chart Amount of methanol is calculated making use of the formula given in the following equation Amount of methanol ¼
The volume of methanol Density of methanol Molar mass of methanol
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
TABLE 12.4
Biodiesel yield for all the 32 trials obtained from design of experiment. Temperature ( C)
Catalyst (wt%)
Reaction time (min)
Stirrer speed (rpm)
Predicted yield (%)
Experimental yield (%)
1
12
56
1.63
150
900
77.61
68.70
2
9
52
1.25
120
800
48.75
39.65
3
9
52
1.25
120
800
48.75
60.21
4
12
56
1.63
90
700
74.55
72.00
5
6
56
1.63
150
700
11.22
9.00
6
9
52
1.25
120
1000
62.41
72.12
7
16
52
1.25
120
800
68.84
79.78
8
12
48
0.88
90
700
78.36
80.00
9
6
48
0.88
90
900
59.15
61.40
10
9
52
2.00
120
800
45.41
50.70
11
6
48
1.63
90
700
46.32
50.78
12
9
52
1.25
120
600
64.44
62.00
13
12
48
1.63
150
700
92.63
90.12
14
6
48
0.88
150
900
66.89
65.00
15
6
56
0.88
150
900
9.43
5.00
16
9
52
0.50
120
800
3.01
5.00
17
6
56
0.88
90
700
54.08
56.00
18
9
52
1.25
120
800
48.75
50.00
19
6
56
1.63
90
900
83.95
82.01
20
9
52
1.25
120
800
48.75
46.90
21
3
52
1.25
120
800
50.57
46.90
22
12
48
0.88
150
900
54.72
50.00
23
9
52
1.25
120
800
48.75
40.60
24
12
56
0.88
150
700
14.18
9.43
25
6
48
0.88
150
700
78.03
80.00
26
12
48
1.63
90
900
77.23
75.00
27
9
52
1.25
60
800
62.80
59.80
28
9
52
1.25
120
800
48.75
47.90
29
9
52
1.25
180
800
42.50
52.78
30
9
45
1.25
120
800
98.49
95.40
31
9
60
1.25
120
800
44.63
55.00
32
12
56
0.88
90
900
12.57
7.80
12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
Molar ratio (methanol:oil)
306
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
Trial No
307
12.9 EXPERIMENTAL METHODOLOGY
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Trial 6
Trial 7
Trial 8
Trial 9
Trial 10
Trial 11
Trial 12
Trial 13
Trial 14
Trial 15
Trial 18
Trial 19
Trial 20
Trial 16
Trial 17
Trial 21
Trial 22
Trial 23
Trial 24
Trial 26
Trial 27
Trial 28
Trial 29
Trial 31
Trial 25
Trial 30
Trial 32
FIGURE 12.3 Photographic views of biodiesel yield obtained from 32 trials.
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308
12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
TABLE 12.5
ANOVA table from design of experiment.
Source
Sum of squares
DF
Mean square
F-value
p-value Prob > F
Model
17954.21
20
897.71
9.7
0.0002
A-temperature
500.6894
1
500.69
5.41
0.0402
B-time
4351.349
1
4351.35
47.01
<0.0001
C-catalyst
2696.216
1
2696.22
29.13
0.0002
D-molar ratio
617.932
1
617.93
6.68
0.0254
Espeed
6.18135
1
6.18
0.067
0.8008
AB
64.08002
1
64.08
0.69
0.4231
AC
1486.103
1
1486.1
16.06
0.0021
AD
348.1956
1
348.2
3.76
0.0785
AE
286.2864
1
286.29
3.09
0.1064
BC
1295.64
1
1295.64
14
0.0033
BD
1289.169
1
1289.17
13.93
0.0033
BE
277.056
1
277.06
2.99
0.1115
CD
11.9025
1
11.9
0.13
0.7267
CE
1807.1
1
1807.1
19.52
0.001
DE
66.9124
1
66.91
0.72
0.4133
A2
219.9673
1
219.97
2.38
0.1514
2
954.1803
1
954.18
10.31
0.0083
2
1103.727
1
1103.73
11.93
0.0054
2
27.93702
1
27.94
0.3
0.5937
2
E
394.7453
1
394.75
4.26
0.0633
Residual
1018.11
11
92.56
Lack of fit
740.5743
6
123.43
2.22
0.1992
Pure error
277.5353
5
55.51
Cor total
18972.32
31
B
C
D
The total concentration of methanol is obtained using the following equation The total concentration of methanol ¼
Amount of methanol The volume of methanol þ Volume of Mahua oil
The concentration of methyl ester is calculated making use of the formula given in the following equation
The concentration of ester ¼
Significant
Not significant
Once the concentration of methyl ester is found from NMR result, a kinetic plot is plotted with time in X-axis and concentration of methyl ester in Y-axis. Linear regression analysis is made use to plot the line between time and methyl ester concentration. The slope of the given line gives the initial methyl ester rate concerning the corresponding reaction temperature. Kinetic analysis is conducted for transesterification reaction at 45, 50, and 55 C. Once the initial methyl ester rate is
The methyl ester signal value Total concentration of methanol Methyl ester signal value þ Methanol signal value
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
309
12.10 RESULTS AND DISCUSSION
obtained for the corresponding reaction temperatures, an Arrhenius plot to find out the activation energy needed for conversion of triglyceride to Fatty Acid Methyl Ester (FAME) or biodiesel is made. Arrhenius plot consists of reciprocal of temperature in the X-axis and the natural logarithm of initial methyl ester rate in the Y-axis.
12.10 RESULTS AND DISCUSSION 12.10.1 Comparision of predicted yield and actual yield The predicted and actual value is shown in Fig. 12.4, and the adjusted R2 value was 0.9294 which denotes 92.94% of the variability. The predicted value and the actual values are reasonably very close to each other and that values are approaching unity. This indicates that the data fit with the model and convincingly good estimate of response for this system. Also, the residuals also validate the corrected model. Residual is a difference between actual and theoretical responses.
12.10.2 Effect of process parameters on biodiesel yield This section describes the interaction effect of transesterification process parameters namely methanol to oil ratio, that is, molar ratio, the catalyst concentration in % w/w, reaction temperature, reaction time, and stirring speed on biodiesel yield. Figs. 12.5e12.14 show the interaction effects of these parameters on biodiesel yield and the same is discussed below.
Fig. 12.5 indicates the graph is drawn to show the effect of molar ratio and temperature on the yield and the maximum yield obtained at a molar ratio of 9:1 and at a temperature of 52.5 C. From the graph, it is observed that yield increases with increase in molar ratio and with a decrease in temperature simultaneously. At higher temperature and at a lower molar ratio lower yield is obtained. Higher molar ratio to reaction temperature that led to the separation of glycerol is complicated, and the yield of biodiesel decreases because a portion of the glycerol remains in the biodiesel phase. Fig. 12.6 indicates the graph plotted to show the effect of molar ratio and catalyst on the yield. From the graph, it is noted that the yield increases as the value of both molar ratio and catalyst increases. For the lower value of catalyst maximum yield occurs at the higher molar ratio and similarly for the lower value of the molar ratio, maximum yield occurs at intermediate catalyst concentration. From the graph, it analyses that maximum yield occurs at the average molar ratio and catalyst concentration. Fig. 12.7 shows the interaction between molar ratio and time to show their effect on yield. From this, at the lower molar ratio and at high reaction time, the transesterification process results in lesser yield and at an intermediate time, and average molar ratio yield is increased. From the graph, it is observed that at low reaction time and yet higher molar ratio maximum yield is obtained. This was mainly due to the transesterification process completed satisfactorily at a lower temperature with enough time in the presence of an alkaline catalyst (sodium methoxide). Fig. 12.8 shows the interaction between molar ratio and speed to show their effect on yield. From this it is
96.00
Predicted yield (%)
73.25
50.50
27.75
5.00 5.00
27.73
50.47 Actual yield (%)
73.20
95.94
FIGURE 12.4 Graphical representation of predicted yield and actual yield.
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
310
12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
Experimental yield
96
81.75
67.5
53.25
39
56.25
12.75 54.38
11.13 52.50
9.50 50.63
B: temperature
7.88
A: molar ratio
48.75 6.25
FIGURE 12.5 Response surface plot of biodiesel yield against molar ratio and temperature.
Experimental yield
80
61.25
42.5
23.75
5
12.75
1.63 1.44
11.13 1.25
C: catalyst
9.50 1.06
7.88
A: molar ratio
0.88 6.25
FIGURE 12.6 Response surface plot of biodiesel yield against molar ratio and catalyst.
concluded that at a constant speed, increase in molar ratio, yield increases up to a certain extent and then it is decreased. It is observed from the graph that at the maximum molar ratio and minimum speed the yield percentage is more. From the observed values, it is noted that maximum yield is obtained at lower values of stirring speed. Further, at the stirring rate above 700 rpm avortex in the liquid phase was createdand lowered its
surface in the central part which resulted in a shorter residence time of methanol bubble in the liquid phase. The residence time of methanol bubble in the liquid phase is important to increase the biodiesel yield. Fig. 12.9 explains the interaction between catalyst concentration and reaction temperature. It is found that at intermediate values of catalyst concentration and lower temperatures, biodiesel yield is maximum.
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
311
12.10 RESULTS AND DISCUSSION
80
Experimental yield
69.5
59
48.5
38
150.00
12.75 135.00
11.13 120.00
9.50 105.00
D: time
7.88
A: molar ratio
90.00 6.25
FIGURE 12.7 Response surface plot of biodiesel yield against molar ratio and time.
Experimental yield
80
69.75
59.5
49.25
39
900.00
12.75 850.00
11.13 800.00
E: speed
9.50 750.00
7.88
A: molar ratio
700.00 6.25
FIGURE 12.8 Response surface plot of biodiesel yield against molar ratio and speed.
From the graph, it is observed that as the temperature increases at constant catalyst concentration, the percentage of biodiesel yield is decreased. This result is due to the negative interaction of reaction temperature and catalyst concentration causes soap formation, which
decreases the yield of biodiesel. The effect of catalyst concentration is more significant than the effect of reaction temperature, but the interaction effect of both the factors is same on the yield. From the figure it is clear that as the temperature increased the amount of yield
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
312
12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
Experimental yield
96 73.25 50.5
27.75 5
56.25
1.63 1.44
54.38 52.50
1.25 1.06
C: catalyst
50.63
B: temperature
0.88 48.75
FIGURE 12.9 Response surface plot of biodiesel yield against temperature and catalyst.
decreased and this is because of triglyceride saponification and the subsequent dissolution of methyl esters into glycerol. Fig. 12.10 indicates that the higher amount of yield occurred with low reaction temperature and at higher reaction time. At higher reaction time and at higher reaction temperature the amount of yield is very less. This is because at higher reaction time and higher reaction temperature the saponification of glycerides gets accelerated by the alkaline catalyst before the completion of transesterification process and also the excessive loss of methanol also leads to decrease in the yield.
Fig. 12.11 points out the interaction between reaction temperature and stirring speed. It indicates that at higher speed and lower temperature the yield obtained is maximum. From the graph, it is clear that at a constant speed as the temperature increases the yield decreases. The main impact of the combination of reaction temperature and stirring speed is that it causes a proper contact between the reagents and the oil during transesterification process. The main reason for the decrease in the amount of yield when temperature and speed increased is because of accelerated saponification reaction. Generally, the impact of stirring speed on the reaction is less and can be neglected.
Experimental yield
96 78.75 61.5 44.25 27
56.25
150.00 54.38
135.00 120.00 D: time
52.50 50.63
105.00
B: temperature
90.00 48.75
FIGURE 12.10
Response surface plot of biodiesel yield against temperature and time. III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
313
12.10 RESULTS AND DISCUSSION
96
Experimental yield
81.75
67.5
53.25
39
900.00
56.25 850.00
54.38 52.50
800.00 750.00
E: speed
50.63
B: temperature
700.00 48.75
FIGURE 12.11 Response surface plot of biodiesel yield against temperature and speed.
61
Experimental yield
47 33 19 5
1.63
150.00 135.00
1.44 120.00
D: time
1.25 105.00
1.06 90.00 0.88
C: catalyst
FIGURE 12.12 Response surface plot of biodiesel yield against catalyst and time.
Fig. 12.12 indicates the interaction between catalyst concentration and reaction time. From the graph it is observed that as the catalyst concentration increased at constant time, the biodiesel yield is increased. At higher catalyst concentration and at lower reaction time, higher biodiesel yield is obtained. From the behavior, it is seen that the equilibrium of the reaction reached rapidly at some point and beyond that point the reaction gets stagnated or starts to reverse. Fig. 12.13 explains the interaction between catalyst and speed. From the graph, it is observed that higher stirring speed and higher catalyst concentration produced the highest yield. As the speed
increases at constant catalyst concentration, there is a significant decrease in biodiesel yield. Fig. 12.14 explains the interaction between reaction time and stirring speed. At higher reaction time and higher stirring speed, the yield of biodiesel decreases. This is due to the conversion of triglyceride to an ester by enhanced reaction time. From these response plots, it was observed that the interaction effects of stirring speed were less significant effect on the yield of biodiesel compared to other parameters in the transesterification process. The same was shown in the ANOVA table where speed was not
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
314
12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
73
Experimental yield
56
39
22
5
900.00
1.63 850.00
1.44 1.25
800.00 750.00
E: speed
1.06
C: catalyst
700.00 0.88
FIGURE 12.13
Response surface plot of biodiesel yield against catalyst and speed.
73
Experimental yield
64.5
56
47.5
39
900.00
150.00 850.00
135.00 120.00
800.00 E: speed
750.00
105.00
D: time
700.00 90.00
FIGURE 12.14
Response surface plot of biodiesel yield against time and speed.
significant, and all other parameters were significant. Similar research was observed from other research findings.
12.10.3 Biodiesel analysis After a transesterification reaction, the analytical technique such as Nuclear Magnetic Resonance (NMR) was used to examine the biodiesel verification to inspect the quality of the biodiesel which was suitable for engine
study. Figs. 12.15 and 12.16 shows NMR plot for raw oil and biodiesel, respectively. Interpretation of NMR was conducted using the database of Center for Advanced Research in Indian System of Medicine (CARISM), SASTRA University. The spectra of known compounds stockpiled in Center for Advanced Research in Indian System of Medicine (CARISM) library was differentiated with the spectra of unknown compounds. By comparing the NMR plots of both raw oil and biodiesel, we can observe that at
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
315
7.264 5.381 5.371 5.362 5.355 5.352 5.344 5.336 5.325 4.322 4.308 4.283 4.269 4.173 4.154 4.134 2.807 2.789 2.771 2.342 2.336 2.317 2.312 2.292 2.286 2.079 2.059 2.038 2.018 2.001 1.605 1.302 1.254 1.001 0.976 0.951 0.902 0.890 0.880 0.867 0.857 0.000
12.10 RESULTS AND DISCUSSION
5
4
3
2
1
ppm
4.15 9.90 10.71 0.49 3.01
6
2.16 2.98
7
1.00
8
0.70 0.73
9
2.30 0.60
10
FIGURE 12.15 NMR plot for raw oil.
3.6 ppm there was a peak in biodiesel which represents the presence of methyl ester and that peak is not present in the raw oil. The peaks obtained at 3.6 ppm in biodiesel NMR plot have shown the confirmation of methyl ester in the obtained biodiesel.
unsaturated and saturated acids obtained from the GC/MS analysis. Saturated fatty acids and methyl esters improve the stability, increase the cloud point and cetane number.
12.10.4 Gas chromatography/mass spectrometer
12.10.5 Physical and chemical properties of biodiesel
The quality of biodiesel is important for engine study and the analytical method like Gas chromatography/Mass spectrometer (GC/MS) were employed to analyze the products of the transesterification reaction. Fig. 12.17 and Table 12.6 show the GC/MS chromatography of biodiesel. For studying the composition of the biodiesel, gas chromatograph or mass spectroscopy was used (PerkinElmer Clarus 500). The column of the capillary (Column id: 250 mm, Column length: 30 m, Capillary Column type: Elite5MS (5% phenyl 95% dimethylpolysiloxane)) was used for examination FAME. The oventemperature of GC was increased to a final temperature of 280 C from an initial temperature of 60 C. The temperature of injection was kept at 280 C; The carrier gas, helium, was used at a flow rate of 1 mL/min. The analysis of mass detector was analyzed by the specified conditions: electron energy of 70 eV, the carriergas (helium). The biodiesel produced from the inedible oil had the
The Physical and chemical properties of produced biodiesel and raw oil were measured. The results of all the tests are provided in Table 12.7.
12.10.6 Experimental procedure for engine study The test engine used was a four-stroke, naturally aspirated, water-cooled, single-cylinder and direct injection compression injection engine. Its compression ratio is 16.7:1. It has a rated power of 3.7 kW at a constant speed of 1500 rpm. The injection timing and injection pressure set by the manufacturer are 23 degrees before TDC and 200 bar, respectively. Fig. 12.18 shows the schematic view of the engine setup used for this study. The test engine used is directly coupled with an eddy current dynamometer to load the engine. A suitable coupling is provided between the engine and generator to achieve the power transmission without any speed reduction.
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
7.280 5.395 5.392 5.380 5.373 5.369 5.361 5.355 5.350 5.343 5.332 5.325 5.306 3.666 3.479 2.827 2.807 2.789 2.771 2.752 2.329 2.304 2.279 2.080 2.060 2.038 2.018 2.000 1.979 1.642 1.619 1.595 1.572 1.304 1.255 1.001 0.976 0.951 0.912 0.901 0.890 0.880 0.867 0.857 –0.00
316
FIGURE 12.16
3
2
1
ppm
2.26 3.26 0.84 2.46 10.58 10.67 0.61 3.00
4
5
1.26
6
7
3.40 2.03
8
9
2.86
10
NMR plot for biodiesel. 15 11×1129 oil sample 26 11 19 29.60 55 29.56 41
100
Scan EI+ TIC 2.80e10
26.56 74
%
0
Time 5.02
FIGURE 12.17
10.02
15.02
20.02
25.02
30.02
35.02
GC/MS chromatography of biodiesel.
The load acting on the engine is varied by changing the current passing through the eddy current dynamometer. A strain gauge which is attached to a torque arm on the dynamometer is used for measuring the force acting on the dynamometer casing from which the torque acting on the dynamometer can be obtained. From this torque, the load acting on the dynamometer, which is same as the load developed by the engine is measured. The load is obtained as the product of torque and angular velocity.
KISTLER quartz transducer was employed to compute the cylinder-pressure. Transducer model 6613 C, with the range of 0e100 bar. The sensor was equipped to measure the in-cylinder pressure in diesel engines. The piezoelectric transducer is selected for accuracy, small size, and its quick response. The transducer should have very high natural frequencies to avoid resonance. The transducer produced a charge output which was relational to the cylinder pressure. The pressure transducer produced electric charge which
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
317
12.10 RESULTS AND DISCUSSION
TABLE 12.6
List of compounds obtained from spectrometry for biodiesel.
S. No.
Peak name
Formula
Molecular weight
Retention time (min)
Peak area
%Peak area
1.
2-Decenal, (Z)
C10H18O
154
12.26
2,557,403
0.7132
2.
2,4-Decadienal, (E,E)-
C10H16O
152
13.06
1,211,714
0.3379
3.
2,4-Decadienal
C10H16O
152
13.61
1,747,760
0.4874
4.
4-Tetradecene, (E)-
C14H28
196
21.77
158,817
0.0443
5.
2-Decene, 9-methyl-, (Z)-
C11H22
154
22.77
130,387
0.0364
6.
Hexadecanoic acid, methyl ester
C17H34O2
270
26.23
1,151,923
0.3212
7.
Palmitic acid
C16H32O2
256
27.46
89,423,504
24.9376
8.
Linoleic acid
C18H32O2
280
30.17
256,056,448
71.4068
9.
Oleic acid
C18H34O2
282
31.59
1,530,239
0.4267
10.
9,17-Octadecadienal, (Z)-
C18H32O
264
33.33
1,407,404
0.3925
11.
Z,Z-3,13-Octadecadien-1-ol
C18H34O
266
33.92
3,212,936
0.8960
TABLE 12.7 S.No.
Properties of diesel, raw oil, and biodiesel. Properties 3
Diesel
Raw oil
Biodiesel
ASTM D6751
1.
Density (kg/m )
824
865
854
D1298
2.
Acid value (mg KOH/g oil)
0
5.34
0.84
D664
3.
0
9
9
D2500
Pour point
( C)
14
5
21
D97
Flash point
( C)
54
321
224
D93
62
334
231
D93
Cloud point
4. 5.
( C)
( C)
6.
Fire point
7.
Kinematic viscosity (cSt)
2.39
25.46
5.11
D445
8.
Calorific value (MJ/Kg)
42
39.66
40.11
D240
9.
Copper strip corrosion
Class 1a
Class 1a
Class 1a
D130
10.
Carbon residue (wt%)
0.0109
0.45
0.2
D189
Fuel flow sensor
Diesel
Bio -diesel
EGR
AVL five gas analyser
Smoke meter
Air flow measurement
Strain guage Calorimeter Surge tank
Orifice plate
Computer UPS
DICI engine
EGR temperature indicator
Crank angle encoder
Coupling
Eddy current dynamometer
FIGURE 12.18 Schematic diagram of the engine experimental setup.
318
12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
was converted to the analog voltage reading with the help of charge amplifier. This charge output was then fed to combustion analyzer to evaluate and determine cylinder combustion characteristics and peak pressure balance. For crank angle measurement KueblerSendix 5000 TDC marker was used. This type of encoder is used wherever engine angle and flow information are needed to calculate the combustion parameters and heat release rate of an engine. The experimental procedure implemented to conduct the test on a diesel engine is discussed in this section. The crank lever was used to start the test engine. The engine was permitted to reach steady-state. The engine cooling was achieved by circulating water through the cylinder head and the jackets of the engine block. SAE 20W-40 oil was used as lubricating oil in a diesel engine. Some trial tests were made to verify, correct, and calibrate all the measuring instruments. The readings were taken thrice to secure repeatability of the data and mean of all three readings were considered in the present investigation. The following biodiesel blends, for example, B100, B40, B20, and B10 were considered based on the literature surveyed for engine study and compared with biodiesel and diesel with standard operating conditions. In order to provide a database to compare test fuels, a thorough investigation on the engine was completed using diesel as the baseline at standard operating conditions (200 bar and 23 bTDC). AVL digas 444 five gas analyzer was used to measure the concentration of CO, CO2, NO, O2, and HC present in the exhaust gas. The concentration of HC and NO are measured in ppm volume, whereas those of CO, CO2, and O2 are expressed regarding percentage volume. For determining the concentration of gaseous pollutants in the exhaust, a sample was taken from a region near to the exhaust valve.
12.10.6.1 Brake thermal efficiency BTE for biodiesel and its blends increases up to the rated load of the engine and then starts decreasing as shown in Fig. 12.19. The maximum BTE for diesel, B10, B20, B40 and B100 was found to be 24.8%, 22.4%, 22.17%, 21.79%, and 21.37%, respectively for 4.0968 BMEP. The variation of BTE was shown in Fig. 12.20 for biodiesel and its blends. Compared to diesel, the BTE was decreased in biodiesel and its blends. The decrease in brake thermal efficiency can be attributed to the fact the calorific value of biodiesel is 40.11 MJ/ kg while that for diesel is 42 MJ/kg. So, with an increase in blending there is a decrease in the calorific value and hence, decrease in BTE.
12.10.6.2 Brake-specific energy consumption (BSEC) Fig. 12.20 shows the variation of BSEC for biodiesel and its blends were compared with diesel. BSEC is the ratio of energy obtained by burning fuel for an hour to brake power. It is an indicator of how effectively the energy obtained from the fuel is. BSEC ¼ Brake specific fuel consumption calorific value of fuel Fig. 12.20 shows that, with an increase in load, the BSEC decreases. At full load condition, the BSEC value is 12.5 MJ/kWh for diesel, 16.04 MJ/kWh for B10 blend, 16.24 MJ/kWh for B20,16.51 MJ/kWh for B40 blend, and for B100 blend it is 16.99 MJ/kWh. At full-load condition, The BSEC for biodiesel and its blends are showing similar value, and it was higher than diesel. The BSEC for B100 is greater than that of diesel, B10, B20, and B40
30
25
BTE(%)
20
15 B100 B40 B20 B10 Diesel
10
5
0 1
2
3
4
5
6
BMEP (bar)
FIGURE 12.19
Variation of brake thermal efficiency for biodiesel and its blends.
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319
12.10 RESULTS AND DISCUSSION
60
B100 B40 B20 B10 Diesel
50
BSEC
40
30
20
10 0
1
2
3
4
5
6
BMEP(bar)
FIGURE 12.20 Variation of brake-specific energy consumption for biodiesel and its blends.
at partial loading condition. BSEC decreased with an increment of blend ratio of diesel at partial loading condition. 12.10.6.3 Heat release rate Fig. 12.21 shows the variation of heat release rate with BMEP. From the figure, it clearly shows that maximum heat release rate occurs for diesel and then it decreases continuously for biodiesel blends and is least for B100. Even though biodiesel has more oxygen content, it cannot produce more energy than diesel. Heat release rate does not depend on only onefactordoxygen content, it also depends on calorific value, C-H value, and latent heat of vaporization. Biodiesel has less calorific value compared to diesel, so the heat release rate for
diesel is higher than that of biodiesel. It is observed that the heat release rate of diesel is 56.8740 J/deg CA at 2 aTDC and for B100 the heat release rate value is 42.530 J/ CA at 7 aTDC. 12.10.6.4 Ignition delay Fig. 12.22 shows a variation of ignition delay with BMEP. From the figure, it is clear that diesel has more delay period compared to biodiesel. Generally, biodiesel has a high cetane number; ignition quality is more because of high cetane number which reduces the delay period. Since diesel has less cetane number ignition delay period will be more as compared to biodiesel. It is observed that at full-load operating condition ignition delay periods for diesel, B10, B20, B40, and
60 B100 B40 B20 B10 Diesel
Heat release rate(J/deg CA)
50 40 30 20 10 0 –10 –40
–20
0t
20
40
Crank Angle(degree)
FIGURE 12.21 Variation of heat release rate for biodiesel and its blends.
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12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
Diesel B10 B20 B40 B100
Ignition duration (degree CA)
20
15
10
5
0 0
1
2
3
4
5
6
BMEP (bar)
FIGURE 12.22
Variation of ignition delay for biodiesel and its blends.
B100 are 13.98 CA, 13.56 CA, 13.31 CA, 13.16 CA, and 13.01 CA, respectively. 12.10.6.5 Cylinder gas peak pressure The peak pressure occurred inside the cylinder during the combustion is termed as cylinder gas peak pressure. Fig. 12.23 shows the comparison of cylinder gas peak pressure for diesel and blends of biodiesel at different loads. From the figure, it is clear that diesel has high peak pressure value compared to biodiesel. The reason behind this statement is diesel has more ignition delay which results in more accumulation of fuel inside the cylinder increase the uncontrolled combustion phase, thus causing high pressure inside the cylinder. It is observed that at full-load condition the peak pressure
values for diesel is 64.85 bar, B10 is 64.13 bar, B20 is 63.757 bar, B40 is 62.116 bar, and for B100 is 60.08 bar, respectively. 12.10.6.6 Combustion duration Fig. 12.24 shows the variation of combustion duration with BMEP. Combustion duration is the one which gives the value of how much duration it took for the complete combustion of fuel. From the figure, it is clear that for all the loads, diesel is having less combustion duration whereas B100 has more combustion duration and also it is clear that as the load increases combustion duration also increases for all the fuel blends. Due to more ignition delay period in diesel, more fuel gets accumulated into the cylinder, and the total fuel is ready for
Cylinder gas peak pressure (bar)
100 B100 B40 B20 B10 Diesel
80
60
40
20
0 0
FIGURE 12.23
1
2
3 BMEP (bar)
4
5
6
Variation of cylinder gas peak pressure for biodiesel and its blends.
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321
12.10 RESULTS AND DISCUSSION
Combustion duration (degree CA)
140 Diesel B10 B20 B40 B100
120 100 80 60 40 20 0 0
1
2
3 4 BMEP (bar)
5
6
FIGURE 12.24 Variation of combustion duration for biodiesel and its blends.
atomization, and also proper mixing takes place, so the combustion duration is less compared to other biodiesel blends, and also as latent heat of vaporization is more for biodiesel compared to diesel, biodiesel takes more time to get vaporized which leads to longer combustion duration compared to diesel. 12.10.6.7 Exhaust gas temperature Fig. 12.25 shows the variation of exhaust gas temperature with BMEP. As the delayed combustion for B100 the exhaust gas temperature higher compared to diesel and other blends. The in-cylinder temperature is comparatively higher for B100 due to higher viscosity and poor atomization causes for delayed combustion, so the temperature carried away by the exhaust gases is more compared to diesel. It is observed at full load operating condition, the exhaust temperatures for diesel,
12.10.6.8 Carbon monoxide Fig. 12.26 shows the variation of carbon monoxide emission with BMEP. Presence of CO indicates incomplete combustion and lack of oxygen for combustion. The initial CO emissions are almost the same for diesel, B10, B20, B40, as well as B100 blends. At full load, the CO emission shows 1.10 vol% for diesel, 1.00 vol% for B10 blend, 0.8 vol% for B20 and 0.76 vol% for B40, 0.72 vol % for B100. The CO emission for B100 is lower than that of B40, B20, and B10 which are lesser than that of diesel. The reason for the decrease in the CO volume can be attributed to the presence of oxygen in biodiesel while diesel has no oxygen content at all. So, as the blending percentage increases, there is comparatively
Diesel B10 B20 B40 B100
200 Exhaust gas temperature (°C)
B10, B20, B40, and B100 are 131.89, 133.91 149.35, 155.45 and 156.09 C, respectively.
150
100
50
0 0
1
2
3 BMEP (bar)
4
5
6
FIGURE 12.25 Variation of exhaust gas temperature for biodiesel and its blends.
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12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
1000
1.2 1.0
B100 B40 B20 B10 Diesel
NO(ppm)
CO (%)
0.8
B100 B40 B20 B10 Diesel
800
0.6
600
400
0.4 200
0.2 0.0 0
1
2
3 BMEP (bar)
4
5
0
6
FIGURE 12.26 Variation of carbon monoxide for biodiesel and its
0
FIGURE 12.28
1
2
3 BMEP(bar)
4
5
6
Variation of nitric oxide for biodiesel and its blends.
blends.
more oxygen available in the engine and combustion becomes more efficient. 12.10.6.9 Carbon dioxide Fig. 12.27 shows the variation of CO2 with BMEP. The CO2 content increases with an increase in load, since with increasing load more fuel will be burnt. The fuel will shift from diesel to B10, B20, B40, and B100 blend; the CO2 volume percentage increases under all operating conditions. At full-load condition, 7.5670 vol% of CO2 is formed in diesel combustion, 10.5 vol%, 10.9 vol %, 10.5 vol%, and 11.1 vol% of CO2 is formed in B10, B20, B40, and B100, respectively. This is because oxygen content is more in biodiesel as a result of which an increase in the biodiesel ratio increased the CO2 formation. 12.10.6.10 Nitric oxide Nitric oxide emission is harmful emission which is produced during the uncontrolled combustion phase.
The NO formation depends upon the availability of oxygen content and the in-cylinder temperature. Fig. 12.28 shows the variation of nitric oxide (NO) emissions with BMEP. As the load increases, NO emissions increase for all the fuels. At full load, NO emissions reached 835 ppm for diesel, 850 ppm for B10, 856 ppm for B20, 864 ppm for B40, and 883 ppm for B100. Thus, NO emission was higher for B100 compared to B40, B20, B10, and diesel. No emission was increased with increase in biodiesel concentration. The premixed combustion is more efficient with an increase in the blending due to a higher amount of oxygen present in the biodiesel. The in-cylinder temperature is comparatively higher due to higher heating and thus NO emissions increase. 12.10.6.11 Unburned hydrocarbons Fig. 12.29 shows the variation of Unburned Hydrocarbon emissions (UBHC) with BMEP. A UBHC emission results from the part of the fuel that does not take part 140
12
B100 B40 B20 B10 Diesel
8
Unburned HC(ppm)
CO2 (%)
10
6 4 2
100 80 60 40 20
0 0
FIGURE 12.27 blends.
B100 B40 B20 B10 Diesel
120
1
2
3 BMEP (bar)
4
5
6
Variation of carbon dioxide for biodiesel and its
0
0
FIGURE 12.29
1
2
3 BMEP(bar)
4
5
6
Variation of unburned hydrocarbons for biodiesel
and its blends.
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323
NOMENCLATURE
in the combustion, that is, complete combustion does not take place. At full load, 122 ppm of UBHC is produced by diesel, 112 ppm by B10, 92 ppm by B20, 89 ppm by B40, and 81 ppm by B100. The higher oxygen content in biodiesel and its blends is the reason for which their combustion is relatively more efficient when compared with pure diesel. As the blending ratio decreases progressively with B10, B20, B40, and B100, the oxygen percentage increases and thus combustion becomes more and more efficient resulting in lower UBHC emissions. 12.10.6.12 Filter smoke number The filtered soot causes blackening of the filter paper, which is measured by a photoelectric measuring head and the result is analyzed by a microprocessor. The determined value is the Filter Smoke Number (FSN). Fig. 12.30 shows the variation of FSN with BMEP. FSN increases with load. FSN is the index which measures the amount of carbon particle (soot) available in the exhaust. The FSN value for diesel is higher than that of B10, B20, B40, and B100 blends. It is due to thisfact combustion is proper as the blending percentage increases. At the rated load, the FSN value for diesel, B10, B20, B40, and B100 are 8.88, 7.486, 7.29, 7.41, and 6.83, respectively. Higher oxygen content and proper combustion will lead to lower smoke emission for biodiesel and its blends compared to diesel.
12.11 CONCLUSIONS The study concentrates on biodiesel production and also concentrates on identifying the optimum conditions. From the study, biodiesel production is optimized through response surface methodology (RSM). The 10
Filter smoke number
8
B100 B40 B20 B10 Diesel
6
4
2
0 0
1
2
3
4
5
6
BMEP(bar)
FIGURE 12.30 and its blends.
Variation of unburned hydrocarbons for biodiesel
performance, combustion, and emission analysis of obtained biodiesel and its blends were carried out by using a single-cylinder four-stroke diesel engine. The following conclusions are drawn from this work, and it is listed below. • The optimal condition for production of methyl ester was the following: temperature 45 C, time 120 min, molar ratio 9:1 (methanol:oil), catalyst concentration 1.25 wt%, and 800 rpm stirrer speed. At this optimized condition, the yield of purified biodiesel was 95.4%. • The acid value of the final biodiesel was estimated as 0.84 mg of KOH/g of oil. Based on that it was concluded that single stage transesterification was enough to produce fatty acid methyl ester (FAME). • It was observed that the brake thermal efficiency of the biodiesel (B100) is 3.5% less as compared to that of diesel. • At rated load, the brake specific energy consumption for B100 is 36% higher than diesel. The brake specific energy consumption decreased with increase in biodiesel blend. • NO emission for biodiesel (B100) was 6% higher than diesel at full-load condition. Similarly, unburnt hydrocarbon and smoke emission were lower than diesel by 22% and 23%, respectively. • It is observed that at full-load conditions, CO2 emissions for biodiesel are 4% higher than diesel and CO emission 0.4% lower than diesel due to higher oxygen concentration resulting in complete combustion of biodiesel.
NOMENCLATURE ANOVA ASTM B100 B20 B50 BSEC BSFC BTE CCD CH3ONa CI CO CO2 DJO DJO10 DLF DoE EGR EGT EN FAAE FAEE
analysis of variance American Society for Testing Material 100% biodiesel 20% biodiesel þ 80% diesel 50% biodiesel þ 50% diesel brake-specific energy consumption brake-specific fuel consumption brake thermal efficiency (%) central composite design sodium methoxide combustion ignition carbon monoxide carbon dioxide Degummed jatropha oil 10% degummed jatropha oil þ 90% diesel diesel-likefuel design of experiment exhaust gas recirculation exhaust gas temperature European norms fatty acyl acid ester fatty acid ethyl ester
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324 FAME FSN GCMS GHG H2SO4 HC JCO JO JO10 KOH LHR LOME NaOH NCV NMR NO NOx OPEC PM REE RME RSM SOx SVO TAG TBC TDC UBHC
12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
fatty acid methyl ester filter smoke number gas chromatography massspectroscopy green house gas sulfuric acid hydrocarbon Jatropha curcas oil jatropha oil 10% jatropha oil þ 90% diesel potassium hydroxide low heat rejection linseed oil methyl ester sodium hydroxide net calorific value nuclear magnetic resonance nitric oxide nitrogen oxides Organization of the Petroleum Exporting Countries particulate matter rapeseed ethyl ester rapeseed methyl ester response surface methodology sulfur dioxides straight vegetable oil triglycerides thermal barrier coating top dead center unburned hydrocarbon (ppm)
Acknowledgments This work was supported by the Department of Science and Technology, New Delhi, India, and the Director, National Institute of Technology, Tiruchirappalli, India for extending the facilities to carry out the research work.
References [1] Khosravi E, Shariati A, Nikou MRK. Instant biodiesel production from waste cooking oil under industrial ultrasonic irradiation. Int J Oil Gas Coal Technol 2016;11(3). [2] Prabhakar S, Banugopan VN, Annamalai K, Jayaraj S. Analysis of chosen parameters of CI engine for nerium oil - an alternative fuel. In: Proceedings of the international conference on frontiers in automobile and mechanical engineering - 2010, FAME-2010; 2010. p. 88e91. [3] The International Energy Agency (IEA). World energy outlook 2006. OECD/IEA; 2006. [4] Kankia AI, Musa A, Daha A, Ishaq U. Production, characterization and process variables of biodiesel from non-edible plant oil (neem &soapnut): a review. Int J Sci Res 2014;3(11). [5] REN21 Renewables 2010 Global Status Report. Renewables 2010 global status report. Paris: REN21 Secretariat; 2010. p. 15. [6] Chhetri AB, Tango MS, Budge SM, Watts KC, Islam MR. Nonedible plant oils as new sources for biodiesel production. Int J Mol Sci 2008;9(2):169e80. [7] Manickam S, Arigela VND, Gogate PR. Intensification of synthesis of biodiesel from palm oil using multiple frequency ultrasonic flow cell. Fuel Process Technol 2014;128:388e93. [8] Lay L, MyintMahmoud M, El-Halwagi. Process analysis and optimization of biodiesel production from soybean oil. Clean Technol Environ Policy 2009;11(3):263e76.
[9] Atabani AE, Ce´sar ADS. Calophyllum inophyllum L. e a prospective non-edible biodiesel feedstock. Study of biodiesel production, properties, fatty acid composition, blending and engine performance. Renew Sustain Energy Rev 2014;37:644e55. [10] Ahmad AL, Yasin NHM, Derek CJC, Lim JK. Microalgae as a sustainable energy source for biodiesel production: a review. Renew Sustain Energy Rev 2011;15(1):584e93. [11] Demirbas A, Bafail A, Ahmad W, Sheikh M. Biodiesel production from non-edible plant oils. Energy Explor Exploit 2016;34:290e318. [12] Devan PK, Mahalakshmi NV. Study of the performance, emission and combustion characteristics of a diesel engine using poon oil-based fuels. Fuel Process Technol 2009;90(4):513e9. [13] Srivastava A, Prasad R. Triglycerides-based diesel fuels. Renew Sustain Energy Rev 2000;4(2):111e33. [14] Ramachandran S, Singh SK, Larroche C, Soccol CR, Pandey A. Oil cakes and their biotechnological applications - a review. Bioresour Technol 2007;98(10):2000e9. [15] Nye MJ, Southwell PH. Esters from rapeseed oil as diesel fuel. In: Proc. Vegetable oil as diesel fuel Seminar III Peoria. IL: Northern Agricultural Energy Centre; 1983. p. 77e83. [16] Cvengros J, Povazanec F. Production and treatment of rapeseed oil methyl esters as alternative fuels for diesel engines. Bioresour Technol 1996;55(2):145e50. [17] Labeckas G, Slavinskas S. The effect of rapeseed oil methyl ester on direct injection Diesel engine performance and exhaust emissions. Energy Convers Manag 2006;47(13e14):1954e67. [18] Rashid U, Anwar F, Moser BR, Knothe G. Moringa oleifera oil: a possible source of biodiesel. Bioresour Technol 2008;99(17): 8175e9. [19] Kafuku G, Mbarawa M. Alkaline catalyzed biodiesel production from moringa oleifera oil with optimized production parameters. Appl Energy 2010;87(8):2561e5. [20] Saydut A, Duz MZ, Kaya C, Kafadar AB, Hamamci C. Transesterified sesame (Sesamum indicum L.) seed oil as a biodiesel fuel. Bioresour Technol 2008;99(14):6656e60. [21] C ¸ aynak S, Gu¨ru¨ M, Bic¸er A, Keskin A, Ic¸ingu¨r Y. Biodiesel production from pomace oil and improvement of its properties with synthetic manganese additive. Fuel 2009;88(3):534e8. [22] De BK, Bhattacharyya DK. Biodiesel from minor vegetable oils like karanja oil and nahor oil. Lipid e Fett 1999;101(10):404e6. [23] Sharma YC, Singh B, Korstad J. Application of an efficient nonconventional heterogeneous catalyst for biodiesel synthesis from pongamia pinnata oil. Energy Fuels 2010;24(5):3223e31. [24] Jain S, Sharma MP. Kinetics of acid base catalyzed transesterification of Jatropha curcas oil. Bioresour Technol 2010;101(20):7701e6. [25] Sahoo PK, Das LM, Babu MKG, Arora P, Singh VP, Kumar NR, et al. Comparative evaluation of performance and emission characteristics of jatropha, karanja and polanga based biodiesel as fuel in a tractor engine. Fuel 2009;88(9):1698e707. [26] Puhan S, Jegan R, Balasubbramanian K, Nagarajan G. Effect of injection pressure on performance, emission and combustion characteristics of high linolenic linseed oil methyl ester in a DI diesel engine. Renew Energy 2009;34(5):1227e33. [27] Ma F, Hanna MA. Biodiesel production: a review. Bioresour Technol 1999;70:1e15. [28] Demirbas A. Biodiesel from vegetable oils via transesterification in supercritical methanol. Energy Convers Manag 2002;43: 2349e56. [29] Vaıtilingom G. Huiles ve´ge´talesdbiocombustible diesel. Influence de la nature des huiles et en particulier de leur composition en acides gras sur la qualite´ -carburant. Universite´ d’Orleans; 1992. [30] Agarwal D, Agarwal AK. Performance and emissions characteristics of jatropha oil (preheated and blends) in a direct injection compression ignition engine. Appl Therm Eng 2007;27: 1314e2323.
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
REFERENCES
[31] Cert A, Moreda W, Perez-Camino MC. Chromatographic analysis of minor constituents in vegetable oils. J Chromatogr A 2000;881:131e48. [32] Gonfa Keneni Y, Mario Marchetti J. Oil extraction from plant seeds for biodiesel production. AIMS Energy 2017;5(2):316e40. Available from: http://www.aimspress.com/article/10.3934/ energy.2017.2.316. [33] Mahanta P, Shrivastava A. Technology development of bio-diesel as an energy alternative. In: Challenges Strategy Sustain Energy Deficiency and Environment; 2012. p. 1e19. Available from: http://www.newagepublishers.com/samplechapter/001305. pdf. [34] Achten WMJ, Verchot L, Franken YJ, Mathijs E, Singh VP, Aerts R, et al. Jatropha bio-diesel production and use. Biomass Bioenergy 2008;32(12):1063e84. [35] Bhargavi G, Nageswara Rao P, Renganathan S. Review on the extraction methods of crude oil from all generation biofuels in last few decades. IOP Conf Ser Mater Sci Eng 2018;330(1). [36] Weiss EA. Oilseed crops. Longman Group Ltd; 1983. p. 31e99. [37] Muzenda E, Kabuba J, Mdletye P, Belaid M. Optimization of process parameters for castor oil production. Proc World Congr Eng 2012;3:5401e14. [38] Atabani AE, Silitonga AS, Ong HC, Mahlia TMI, Masjuki HH, Badruddin IA, et al. Non-edible vegetable oils: a critical evaluation of oil extraction, fatty acid compositions, biodiesel production, characteristics, engine performance and emissions production. Renew Sustain Energy Rev 2013;18:211e45. Available from: http://linkinghub.elsevier.com/retrieve/pii/ S1364032112005552. [39] Verdugo C, Luna D, Posadillo A, Sancho ED, Rodrı´guez S, Bautista F, et al. Production of a new second generation biodiesel with a low cost lipase derived from Thermomyces lanuginosus: optimization by response surface methodology. Catal Today 2011:107e12. [40] Meher LC, Vidya Sagar D, Naik SN. Technical aspects of biodiesel production by transesterificationda review. Renew Sustain Energy Rev 2006;10:248e68. [41] Balat M, Balat H. Progress in biodiesel processing. Appl Energy 2010;87:1815e35. [42] Gurunathan B, Ravi A. Process optimization and kinetics of biodiesel production from neem oil using copper doped zinc oxide heterogeneous nanocatalyst. Bioresour Technol 2015;190:424e8. [43] Latchubugata CS, Kondapaneni RV, Patluri KK, Virendra U, Vedantam S. Kinetics and optimization studies using Response Surface Methodology in biodiesel production using heterogeneous catalyst. Chem Eng Res Des July 1, 2018;135:129e39. Available from: https://www.sciencedirect.com/science/article/pii/ S0263876218302612. [44] Muthukumaran C, Praniesh R, Navamani P, Swathi R, Sharmila G, Manoj Kumar N. Process optimization and kinetic modeling of biodiesel production using non-edible Madhuca indica oil. Fuel 2017;195:217e25. [45] Ma Y, Wang Q, Sun X, Wu C, Gao Z. Kinetics studies of biodiesel production from waste cooking oil using FeCl3-modified resin as heterogeneous catalyst. Renew Energy 2017;107:522e30. [46] Ullah Z, Bustam MA, Man Z, Khan AS, Muhammad N, Sarwono A. Preparation and kinetics study of biodiesel production from waste cooking oil using new functionalized ionic liquids as catalysts. Renew Energy 2017;114:755e65. [47] Sidibe´ SS, Blin J, Vaitilingom G, Azoumah Y. Use of crude filtered vegetable oil as a fuel in diesel engines state of the art: literature review. Renew Sustain Energy Rev 2010;14(9): 2748e59. [48] Higelin P. Huiles ve´ge´talesdbiocombustible diesel. Incidence des aspects thermiques lie’ s au type de moteur sur la combustion. Orle´ans: Universite´ d’Orle´ans; 1992.
325
[49] Sirisomboon P, Kitchaiya P, Pholpho T, Mahuttanyavanitch W. Physical and mechanical properties of Jatropha curcas L. fruits, nuts and kernels. Biosyst Eng 2007;97:201e7. [50] Openshaw K. A review of Jatropha curcas: an oil plant of unfulfilled promise. Biomass Bioenergy 2000;19:1e15. [51] Sidibe´ SS, Blin J, Vaitilingom G, Azoumah Y. Use of crude filtered vegetable oil as a fuel in diesel engines state of the art: literature review. Renew Sustain Energy Rev 2010;14:2748e59. [52] Van Grepen J. Cetane number testing of biodiesel. In: Proceedings from the 3rd liquid fuels and industrial products from renewable resources conference; 1996. [53] Ramadhas AS, Jayaraj S, Muraleedharan C. Use of vegetable oils as I.C. engine fuelsda review. Renew Energy 2004;29:727e42. [54] Murugesan A, Umarani C, Subramanian R, Nedunchezhian N. Bio-diesel as an alternative fuel for diesel enginesda review. Renew Sustain Energy Rev 2008. [55] Labeckas G, Slavinskas S. Performance of direct-injection offroad diesel engine on rapeseed oil. Renew Energy 2006;31: 849e63. [56] Zhu RJ, Wang XB, Miao H, Huang ZH. Combustion and particulate emission characteristics of a diesel engine fuelled with diesel-dimethoxymethane blends. Proc Inst Mech Eng - Part D J Automob Eng 2010;224(4):521e31. [57] Adaileh WM, Alqdah KS. Performance of diesel engine fuelled by a biodiesel extracted from a waste cocking oil. In: Energy procedia; 2012. p. 1317e34. [58] Devan PK, Mahalakshmi NV. Combustion, emission and performance characteristics of diesel engine fueled with Eucalyptus oil with an ignition enhancer. Int J Green Energy 2010;1(1):40e9. [59] Hassan MH, Kalam MA. An overview of biofuel as a renewable energy source: development and challenges. In: Procedia engineering; 2013. p. 39e53. [60] Ghorbani A, et al. A comparative study of combustion performance and emission of biodiesel blends and diesel in an experimental boiler. Appl Energy 2011;88:4725e32. [61] Huang D, Zhou H, Lin L. Biodiesel: an alternative to conventional fuel. In: Energy procedia; 2011. p. 1874e85. [62] Mostafa SSM, El-Gendy NS. Evaluation of fuel properties for microalgae Spirulina platensis bio-diesel and its blends with Egyptian petro-diesel. Arab J Chem 2017;10:S2040e50. [63] Pradhan P, Chakraborty S, Chakraborty R. Optimization of infrared radiated fast and energy-efficient biodiesel production from waste mustard oil catalyzed by Amberlyst 15: engine performance and emission quality assessments. Fuel 2016;173:60e8. [64] Prabhahara M, Rajanb K, Krishnamoorthi S. Performance and emission characteristics of diesel engine with mustard oildiesel blends as fuel. Int J Chem Sci 2016;14(S2):655e64. [65] Kalam MA, Husnawan M, Masjuki HH. Exhaust emission and combustion evaluation of coconut oil-powered indirect injection diesel engine. Renew Energy 2003;28(15):2405e15. [66] Tippayawong N, Permsuwan A, Vorayos N, Kiatsiriroat T, Uppakam S, Panyacum M. Long term direct injection diesel engine operation on vegetable oil/diesel blends. SAE Tech Pap 2003. [67] Bari S, Yu CW, Lim TH. Performance deterioration and durability issues while running a diesel engine with crude palm oil. Proc Inst Mech Eng Part D 2002;216:785e92. [68] Nettles-Anderson S, Olsen D. Survey of straight vegetable oil composition impact on combustion properties. SAE Tech Pap 2009:1e487. [69] Murugesan A, Umarani C, Subramanian R, Nedunchezhian N. Bio-diesel as an alternative fuel for diesel engines-A review. Renew Sustain Energy Rev 2009;13:653e62. [70] Schlick ML, Hanna MA, Schinstock JL. Soybean and sunflower oil performance in a diesel engine. Trans Am Soc Agric Eng 1988;31(5).
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
326
12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
[71] Machacon HTC, Matsumoto Y, Ohkawara C, Shiga S, Karasawa T, Nakamura H. The effect of coconut oil and diesel fuel blends on diesel engine performance and exhaust emissions. JSAE Rev 2001;22(3):349e55. [72] Reksowardojo IK, Lubis IH, Manggala W, Brodjonegoro TP, Soerawidjaja TH, Arismunandar W, et al. Performance and exhaust gas emissions of using biodiesel fuel from physic nut (Jatropha curcas L.) oil on a direct injection diesel engine (DI). SAE Tech Pap 2007:1232e6. [73] Agarwal D, Kumar L, Agarwal AK. Performance evaluation of a vegetable oil fuelled compression ignition engine. Renew Energy 2008;33(6):1147e56. [74] Agarwal AK, Dhar A. Performance, emission and combustion characteristics of jatropha oil blends in a direct injection CI engine. SAE Tech Pap 2009. [75] Singh SP, Singh D. Bio-diesel production through the use of different sources and characterization of oils and their esters as the substitute of diesel: a review. Renew Sustain Energy Rev 2010;14:200e16. [76] Agarwal AK, Dhar A. Experimental investigations of engine durability and lubricating oil properties of jatropha oil blends fuelled Dl diesel engine. In: Proceedings of the ASME internal combustion engine division fall technical conference 2009; 2009. p. 137e47. [77] Anand R, Kannan GR, Nagarajan S, Velmathi S. Performance emission and combustion characteristics of a diesel engine fueled with biodiesel produced from waste cooking oil. SAE Tech Pap 2010. [78] Rakopoulos CD, Hountalas DT, Zannis TC. Theoretical study concerning the effect of oxygenated fuels on di diesel engine performance and emissions. SAE Tech Pap 2004. [79] Lapuerta M, Armas O, Rodrı´guez-Ferna´ndez J. Effect of biodiesel fuels on diesel engine emissions. Prog Energy Combust Sci 2008;34:198e223. [80] Masjuki H, Abdulmuin MZ, Sii HS. Investigations on preheated palm oil methyl esters in the diesel engine. Proc Inst Mech Eng Part A 1996;210(2). [81] Yucesu HS, Ilkilic C. Effect of cotton seed oil methyl ester on the performance and exhaust emission of a diesel engine. Energy Sources Part A 2006;28(4):389e98. [82] Srinivasa Rao P, Gopalakrishnan VK. Vegetable oils and their methyl esters as fuels for diesel engines. Ind J Technol 1991;29: 292e7. [83] Ahmed MA, Ejim CE, Fleck BA, Amirfazli A. Effect of biodiesel fuel properties and its blends on atomization. SAE Tech Pap 2006;2006(724). [84] Tat ME, Van Gerpen JH, Soylu S, Canakci M, Monyem A, Wormley S. Speed of sound and isentropic bulk modulus of biodiesel at 21 C from atmospheric pressure to 35 MPa. J Am Oil Chem Soc 2000;77(3):285e9. [85] Oman H. Energy sources for the world’s post-petroleum era. IEEE Aerosp Electron Syst Mag 2003;18:35e9. [86] Raheman H, Ghadge SV. Performance of diesel engine with biodiesel at varying compression ratio and ignition timing. Fuel 2008;87(12):2659e66. [87] Raheman H, Ghadge SV. Performance of compression ignition engine with mahua (Madhuca indica) biodiesel. Fuel 2007;86(16): 2568e73. [88] Usta N. An experimental study on performance and exhaust emissions of a diesel engine fuelled with tobacco seed oil methyl ester. Energy Convers Manage 2005;46:2373e86. [89] Thornton M. Fuel effects issues for in-use diesel applications. In: Presented at. NAMVECC conference. Chattanooga [TN]; November 4, 2003. p. 104.
[90] McCormick RL, Alvarez JR, Graboski MS. NO x solutions for biodiesel NOx solutions for biodiesel final report. Contract 2003; 1e49. [91] Islam MA, Ayoko GA, Brown R, Stuart D, Heimann K. Influence of fatty acid structure on fuel properties of algae derived biodiesel. In: Procedia engineering; 2013. p. 591e6. [92] Knothe G. Improving biodiesel fuel properties by modifying fatty ester composition. Energy Environ Sci 2009;2(7):759. [93] Puhan S, Vedaraman N, Sankaranarayanan G, Ram BVB. Performance and emission study of Mahua oil (madhuca indica oil) ethyl ester in a 4-stroke natural aspirated direct injection diesel engine. Renew Energy 2005;30(8):1269e78. [94] Sethi VP, Salariya KS. Exhaust analysis and performance of a single cylinder diesel engine run on dual fuels. J Inst Eng Mech Eng Div 2004;85(1 Apr):1e7. [95] Ramadhas AS, Muraleedharan C, Jayaraj S. Performance and emission evaluation of a diesel engine fueled with methyl esters of rubber seed oil. Renew Energy 2005;30(12):1789e800. [96] Agarwal AK, Das LM. Biodiesel development and characterization for use as a fuel in compression ignition engines. J Eng Gas Turbines Power 2001;123(2):440. [97] Tatarnikov AP, Shustrov FA, Lezhnev LY, Petrichenko DA, Papkin IA. Combined supercharging systems and downsizing as the modern trends in the development of vehicle engines. Int J Appl Eng Res 2016;11(22):10975e9. ISSN 09734562. [98] Hu B, Turner JWG, Akehurst S, Brace C, Copeland C. Observations on and potential trends for mechanically supercharging a downsized passenger car engine:a review. Proc Inst Mech Eng - Part D J Automob Eng 2017;231:435e56. [99] Giakoumis EG. Review of some methods for improving transient response in automotive diesel engines through various turbocharging configurations. Front Mech Eng 2016;2. [100] Colban WF, Miles PC, Oh S. Effect of intake pressure on performance and emissions in an automotive diesel engine operating in low temperature combustion regimes. SAE: 2007:01-4063. 2007. [101] Karabektas M. The effects of turbocharger on the performance and exhaust emissions of a diesel engine fuelled with biodiesel. Renew Energy 2009;34(4):989e93. [102] Al-Hinti I, Samhouri M, Al-Ghandoor A, Sakhrieh A. The effect of boost pressure on the performance characteristics of a diesel engine: a neuro-fuzzy approach. Appl Energy 2009;86(1): 113e21. [103] Nayak SK, Pattanaik BP. Experimental investigation on performance and emission characteristics of a diesel engine fuelled with mahua biodiesel using additive. In: Energy procedia; 2014. p. 569e79. [104] Jawre SS, Bhagat A, Moghe SM, Pakhale VA. Diethyl ether as additive and its effect on diesel engine performance e areview. Global Res Dev J Eng 2016;1(5). [105] Arpa O, Yumrutas R, Demirbas A. Production of diesel-like fuel from waste engine oil by pyrolitic distillation. Appl Energy 2010; 87(1):122e7. [106] Guan G, Kusakabe K, Yamasaki S. Tri-potassium phosphate as a solid catalyst for biodiesel production from waste cooking oil. Fuel Process Technol 2009;90(4):520e4. [107] Heywood JB. Internal combustion engine fundamentals. McGrawHill series in mechanical engineering, vol. 21; 2011. 930 p. [108] Tuteja AD, Hoffman MB, Lopez-Crevillen JM, Singh S, Stomber RR, Wallace GC. Selection and development of a particulate trap system for a light duty diesel engine. SAE Technical Paper 920142. 1992.
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
FURTHER READING
[109] Bhaskar T, Nagalingam B, Gopala Krishan KV. The effect of two ignition improving additives on the performance of jatropha oil in low heat rejection diesel engine. In: 4th international conference on small engines and their fuels, Thailand; 1993. p. 14e9. [110] Agarwal D, Agarwal AK. Performance and emissions characteristics of jatropha oil (preheated and blends) in a direct injection compression ignition engine. Appl Therm Eng 2007;27(13): 2314e23. [111] Hulwan DB, Joshi SV. Performance, emission and combustion characteristic of a multicylinder DI diesel engine running on diesel-ethanol-biodiesel blends of high ethanol content. Appl Energy 2011;88(12):5042e55. [112] Rao PV. Experimental investigations on the influence of properties of jatropha biodiesel on performance, combustion, and emission characteristics of a DI-CI engine. World Acad Sci Eng Technol 2011;5(3):629e42. [113] Senthil Kumar R, Manimaran R. Performance and emission characteristics on 4-stroke single cylinder C. I. Engine using cottonseed bio fuels. Asian J Eng Res 2013. ISSN-2319e2100. [114] Chukwuezie OC, Nwaigwe KN, Asoegwu SN, Anyanwu EE. Diesel engine performance of jatropha biodiesel: a review. Biofuels 2014;5(4):415e30. [115] Bechtsis D, Tsolakis N, Vlachos D, Srai JS. Intelligent autonomous vehicles in digital supply chains: a framework for integrating innovations towards sustainable value networks. J Clean Prod 2018;181:60e71. [116] Lkili C, Aydin H. The harmful effects of diesel engine exhaust emissions. Energy Sources Part A 2012;34(10):899e905. [117] Smith OI. Fundamentals of soot formation in flames with application to diesel engine particulate emissions. Prog Energy Combust Sci 1981;7(4):275e91.
327
[118] Tree DR, Foster DE. Optical measurements of soot particle size, number density, and temperature in a direct injection diesel engine as a function of speed and load. SAE Tech Pap 1994. [119] Pu X, Cai Y, Shi Y, Wang J, Gu L, Tian J, et al. Diesel particulate filter (DPF) regeneration using non-thermal plasma induced by dielectric barrier discharge. J Energy Inst 2017:1e13. [120] Environmental Protection Agency (EPA). Nitrogen oxides (NOx), why and how they are controlled. Epa-456/F-99-006R. 1999. [121] Bady MF, Hassanien HM, Mousa SAS, M Hussein A, ElDean AMK. Study of the effects of using acetic acid in condenser de-scaling on the exhaust emissions and the performance of assiut thermal power plant. J Eng Sci 2013;41(3):971e96. [122] Liberman MA. Combustion and environmental concerns. In: Introduction to physics and chemistry of combustion. Berlin, Heidelberg: Springer; 2008. p. 335e41. [123] Ullman TL. Investigation of the effects of fuel composition on heavy-duty diesel engine emissions. SAE Paper 892072. 1989. [124] Lee R, Pedley J, Hobbs C. Fuel quality impact on heavy duty diesel emissionsda literature review. SAE Paper 982649. 1998. [125] Tree DR, Svensson KI. Soot processes in compression ignition engines. Prog Energy Combust Sci 2007;33:272e309.
Further reading [1] Ejigu A, Asfaw A, Asfaw N, Licence P. Moringa stenopetala seed oil as a potential feedstock for biodiesel production in Ethiopia. Green Chem 2010;12(2):316. [2] Sakai T, Kawashima A, Koshikawa T. Economic assessment of batch biodiesel production processes using homogeneous and heterogeneous alkali catalysts. Bioresour Technol 2009;100(13):3268e76.
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12 Performance, combustion, and emission characteristics of DI diesel engine using mahua biodiesel A. Santhoshkumar, Vinoth Thangarasu, R. Anand Department of Mechanical Engineering, National Institute of Technology, Tiruchirappalli, Tamil Nadu, India
O U T L I N E 12.1 Introduction
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12.2 Selection of feedstock
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12.3 Oil extraction
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12.4 Transesterification
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12.7.3 Engine and fuel modification 12.7.3.1 Forced intake air pressure 12.7.3.2 Fuel modification 12.7.3.3 Engine modification 12.8 Engine exhaust emissions 12.8.1 Formations of emissions
12.5 Chemical kinetics of biodiesel production from inedible seeds 296 12.6 Physicochemical properties of SVOs 12.6.1 Chemical characterization 12.6.1.1 Fatty acids 12.6.1.2 Phospholipid content 12.6.1.3 Waxcontent 12.6.1.4 Peroxide value 12.6.2 Physical characteristics 12.6.2.1 Kinematic viscosity 12.6.2.2 Net calorific value 12.6.2.3 Cetane number 12.6.2.4 Density 12.6.2.5 Flashpoint
296 297 297 297 297 297 297 297 297 297 298 298
12.7 Alternate fuels in compression ignition engines 298 12.7.1 Application of unmodified vegetable oils in diesel engine 298 12.7.1.1 Use of neat vegetable oils in diesel engine 298 12.7.1.2 Use of neat vegetable oil blends in diesel engine 298 12.7.2 Use of biodiesel and its blends 299
Advanced Biofuels https://doi.org/10.1016/B978-0-08-102791-2.00012-X
301 301 301 302 302 302
12.9 Experimental methodology 303 12.9.1 Solvent-assisted oil extraction 303 12.9.2 Biodiesel synthesis 303 12.9.2.1 Esterification 303 12.9.2.2 Design of experiments 304 12.9.2.3 Transesterification 304 12.9.2.4 Biodiesel optimization 304 12.9.2.5 Evaluation of the model and analysis for a variance for biodiesel 304 12.9.2.6 Experimental procedure for kinetics study 305 12.10 Results and discussion 12.10.1 Comparision of predicted yield and actual yield 12.10.2 Effect of process parameters on biodiesel yield 12.10.3 Biodiesel analysis 12.10.4 Gas chromatography/mass spectrometer 12.10.5 Physical and chemical properties of biodiesel 12.10.6 Experimental procedure for engine study 12.10.6.1 Brake thermal efficiency
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12.10.6.2 Brake-specific energy consumption (BSEC) 12.10.6.3 Heat release rate 12.10.6.4 Ignition delay 12.10.6.5 Cylinder gas peak pressure 12.10.6.6 Combustion duration 12.10.6.7 Exhaust gas temperature 12.10.6.8 Carbon monoxide 12.10.6.9 Carbon dioxide 12.10.6.10 Nitric oxide
318 319 319 320 320 321 321 322 322
12.1 INTRODUCTION In the current situation the demand for petroleum has increased due to globalization and industrialization. Engineers, researchers, and scientists are trying to find alternative sources due to the rapid rise in fossil fuel prices and its limited availability. Recently, developing countries like India and China are facing an exponential increase in energy need [1]. In contrast, some of the world’s biggest producers of oil are experiencing political instabilitydue to wars. The global demand for oil will grow from 98 M barrels per day in 2015 to 118 M barrels in a day in 2030. Hence, to meet the predicted increase in oil demand, total petroleum supply in 2030 will have to increase 98 M barrels in a day in 2015 to 118 M barrels per day in 2030. Members of OPEC are expected to provide 14.6 M barrels per day of the increase. Right now, petroleum use in the world is 98 M barrels of oil in a day [2,3]. Diminishing fossil fuel resources have fueled research interest in alternative energy sources. The resources for this renewable energy should be naturally replenished such as wind, hydro, and solar, geothermal, biomass. In that biomass is one of the primary and promising alternatives from this renewable energy sources. Biomass is the biological material obtained from live organisms. Biomass could be transformed into different usable forms of transportation fuels like biogas, ethanol, and biodiesel. The biodiesel is generally derived from edible and inedible biomass sources. The biodiesel obtained from edible oil is not economically viable, since it is depleting of food-grade additives and may cause a negative impact on the world [4,5]. The first diesel engine was invented by using peanut vegetable oil as the working fluid. This thought and research led an idea to go for biodiesel which could be prepared from edible and inedible oils. The importance of inedible oil resources is getting attention throughout the world. The reasons for that are readily available in most of the world, particularly wastelands that are unsuitable for cultivating food crops, remove struggle for
12.10.6.11 Unburned hydrocarbons 12.10.6.12 Filter smoke number
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12.11 Conclusions
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Nomenclature
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Acknowledgments
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References
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Further reading
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food, produce valuable byproducts more efficient, more environmentally friendly, and they are more economic related to edible oils. Biodiesel is a promising ecofriendly alternative to fossil fuel. Many renewable sources, including recycled or used oil like waste oil, can be utilized as feedstock. The significance of biodiesel is its ability to be used as a replacement for petroleumbased diesel. Even though the biodiesel production can only take the place of a slight percent of the country’s fuel source, the petroleum market has a proclivity to be easily affected by the alterations in supply [6,7]. Sulfur is one of the critical pollutants present in diesel fuel. High sulfur content in the fuel causes low-level pollution such as smog and affects the environment severely. Diesel fuel sulfur amount falls within the range of 300e500 ppm and has not been managed till lately. Taking away sulfur content from the diesel enormously reduces the lubricity of fuels. Engine efficiency decreases significantly with the reduction of sulfur content, and for improving the lubricities, additives are added to the fuels and lubricating oil. It has been determined that blending ultralow sulfur diesel with biodiesel improves the lubricity which was lost. So, the use of additives to recover lubricity and the additional device to regulate diesel particulate emissions can be avoided using biodiesel [8]. In an effort to decrease reliance on foreign oil, the United States Federal Government has been supportive of growth in the biodiesel industry. Commonly, biodiesel is a mono-alkyl ester which can be synthesized from vegetable oils or animal fats [9,10]. Chemically, biodiesel can be expressed as the mixture of fatty acid alkyl esters (FAAEs). Generally, fatty acid ethyl esters or fatty acid methyl esters (FAEEs and FAMEs) are obtained by the alcoholysis of triacylglycerols (TAGs) from animal fat and vegetable oils with ethanol or methanol. Alkyl esters are formed when triglycerides are reacting with alcohol with the aid of a catalyst. Catalysts which may be either acid or base depending on the process followed in alcoholysis can be homogeneous (single phase) or heterogeneous (more than one phase), and the
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12.2 SELECTION OF FEEDSTOCK
enzyme-catalyzed alcoholysis uses lipases as catalysts. Generally, alcoholysis can be done without the catalyst in which reactions occur at elevated temperatures and pressures. This noncatalyzed alcoholysis still does not have any practical application [11]. Transesterification process was first proposed by Patrick Duffy in the year 1853. In 1893, the earliest diesel engine was invented by Rudolf Diesel and the fuel which was used in the engine was biodiesel produced from peanut. In earlier 1920s and 1930s and later during the Second World War, most countries focused on utilizing vegetable oils as an alternative fuel for CI engine applications. Biodiesel is chemically defined as mono-alkyl ester according to the National Biodiesel Board (USA). Ahmad et al. [10] showed that the liquid-esterebased oxygenated fuel was identical to the petroleum-based diesel fuel but was formed from bioproducts, either animal fats or plant oils. Although biodiesel has many advantages when compared to petroleum-based diesel, the important barrier to its commercial use is the high price for its production. Generally, the cost of feedstock alone consumes 70%e95% of the total biodiesel production cost. Many such alternative fuels have been identified and tested successfully in the past in the diesel engines with and without engine modifications. As each alternative fuel, suggested by researchers has one or a few undesirable characteristics, this prevents the complete substitution of alternative fuels in the place of the existing one. However, still, the search is on to find out the best alternative fuel for the existing diesel fuel. The researchers have adopted the various admission techniques to apply a more substantial fraction of alternative fuels in the existing engines. Many researchers have proved that the identified alternative fuels are partial substitutes for the existing fuels due to their undesirable characteristics [12]. Among alternative fuels, biodiesel has been identified as a versatile fuel to be used in a diesel engine. The methyl esters produced from vegetable oils are unable to compete with diesel fuel due to its cost [13]. Moreover, enough quantity of oils is not produced in the nation to meet its cooking needs. Hence Planning Commission Committee on Development of Biofuel, in its report in the year 2004, noted that inedible oilseeds have to be used for the production of biodiesel. It also suggested that 20% blending of biodiesel with a conventional diesel could save over 13 billion tons of petroleumderived diesel. It is estimated that for every ton of biodiesel production, two tons of oil cakes are produced. Oil cakes are obtained as the residues after the oil is extracted from the seeds. Oil cakes are classified as edible and inedible. Edible oil cakes have substantial protein content with proper nutrients. The composition of oil cakes changes due to local conditions, variety, and extraction procedures. Edible oil cakes are fed to
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animals. Inedible oil cakes are used as fertilizers. Various research works have been focused on oil cakes to produce industrial bioproducts and other valueadded chemicals. The oil cakes possess good energy content, and their enormous availability can make biodiesel more cost-effective. Hence oil cakes can be exploited to produce biofuels [14]. Hence focus was on utilizing oil cakes, biomass which is available in plenty, but also cheap to be utilized for biofuel production.
12.2 SELECTION OF FEEDSTOCK The inedible feedstocks are naturally available abundantly in a particular region. In Europe, sunflower and rapeseeds are used, and in USA soya been and animal fats are used. Conversion of oil into biodiesel has been initiated by many researchers all over the world. Numerous feedstocks have been investigated for their suitability and compatibility of internal combustion engines. The consensus of oil research works is the reliance on the transesterification of oil using suitable alcohol under certain conditions of pressure and temperature. Recently research work is further focused on the optimization method to get maximum yield. Nye and Southwell [15] have synthesized the rapeseed methyl ester with an optimized condition of 1:6 ratio of oil methanol and 1 wt% of NaOH catalyst concentration. Cvengros and Povazanec [16] experimented the two-step transesterification process of cold-pressed rapeseed oil with methanol at 70 C. The performance of neat rapeseed oil methyl eater (RME) and 5%, 10%, 20%, and 35% blends of RME with diesel was reported by Labeckas and Slavinskas [17]. The maximum torque and power of 273.5 and 281 g/kWh were obtained for rapeseed methyl ester which is 18.7% and 23.2% higher than diesel, respectively. The maximum brake thermal efficiency in the range of 36%e40% was obtained for rapeseed methyl ester which is comparable to diesel fuel. The production of biodiesel from Moringa oleiferawas reported by Rashid et al. [18], using a two-step transesterification method. Viscosity, cetane number, cloud point, pour point, oxidative stability, and lubricity were determined in that study. The viscosity, oxidative stability, cetane number were reported as 4.83 mm2/s at 40 C, 3.61 h, and 67, respectively. The alkaline catalytic transesterification of the M. oleifera oil and an optimum biodiesel yield of 82% were reported. Kufuku and Mbarawa, after optimization of the process parameters such as 1 wt% catalyst, 30 wt% methanol, and 60 C reaction temperature[19]. Production of Moringa stenopetala methyl ester was conducted with ethanol, methanol, and a 1:1 ratio of ethanol and methanol with 1:6 ratio of oil to alcohol.
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The physicochemical properties of the Moringa esters were estimated to assess its desirability to utilize in standard diesel engines. The physicochemical characteristics of the ester mixture of M. stenopetala oil were better than that of methyl ester. Sesame seed oil was obtained in 58 w/w%, by traditional solvent extraction, and this oil has good yield when compared with all other seeds. The transesterification of sesame oil (Sesamum indicum L.) carried out to produce methyl ester with a molar ratio as 6:1, using 1.5 g NaOH as a catalyst, was reported by Saydut et al. [20]. The maximum pomace methyl ester yield was achieved with NaOH catalyst and 1:8 ratio of oil to methanol at 60 C temperature for 1 h reaction time. The study also reported the use of synthetic manganese additives to improve fuel properties [21]. A maximum Croton megalocarpus biodiesel yield of 95% was obtained using SiO2 as a superacid solid catalyst. Free fatty acid value of C. megalocarpus oil is found to be too high compared to other feedstocks, so single-step transesterification could not be possibly reported by Kafuku and Mbarawa [19]. The physicochemical properties such as density, viscosity, flash point, pour point and cetane index, and calorific value of biodiesel produced from Mesuaferrea and Pongamia pinnata were assessed. M.ferrea biodiesel is found to be superior to P. pinnata biodiesel reported by De and Bhattacharyya [22]. The transesterification of P. pinnata oil expelled from the seeds was reported by Sharma et al. [23]. Both alkaliand acid esterification were eventually carried out to obtain the final product. Regarding yield, sodium hydroxide was found to be a more acceptable catalyst than potassium hydroxide. Maximum methyl ester yield of 89.5% was attained with oil to methanol ratio of 1:8 and 1:9 for acidcatalyzed transesterification and base-catalyzed esterification, respectively. The physicochemical properties of oil and methyl ester were determined to satisfy ASTM D6751 standard and utilize the biodiesel in an unmodified diesel engine. Jain and Sharma [24] conducted the kinetic study of Jatropha curcas oil (JCO) with esterification (H2SO4) and followed by the base (NaOH)-catalyzed transesterification. They were conducted at an optimum operating temperature of 50 C and 65 C for transesterification and esterification, respectively. The process was carried out with the most favorable oil to methanol ratio of 7:3 (v/v) and 1% of catalyst concentration (w/w) for both H2SO4 and NaOH. The maximum yield of 90.1% during transesterification and about 21.2% of methyl ester during esterification of pretreated JCO were attained. Performance analysis of neat biodiesel synthesized from karanja, jatropha, polanga, and their blends (B20 and B50) at a different speed in a three-cylinder tractor engine at full and part throttle operations was made
by Sahoo et al. [25]. BSFC for all the biodiesel blends was higher compared to neat diesel operation. The engine power increases with increasing the jatropha biodiesel concentration, and maximum power is obtained for B50 at the rated speed of 2200 rpm. The effect of using linseed oil methyl ester having high linolenic acid in diesel engine was investigated by Puhan et al. [26]. The biodiesel shows the lower brake thermal efficiency compared to diesel due to higher oxides of nitrogen in a constant speed compression ignition engine has a capacity of 4.4 kW. In comparison to the conventional process, the energy requirement of 41.5% could be saved from the proposed biodiesel process. The catalyst is generally used to increase the rate of reaction for the chemical process which was started by Ma and Hanna [27]. In general, there are two types of catalyst involved in this chemical process. One is a homogeneous catalyst in which only one phase component and the other is heterogeneous which involves two or more than two phases. Homogenous catalyst provides fast reaction rate compared to the heterogeneous catalyst, but it is difficult to separate from the reaction mixture. Catalytic reaction of heterogeneous catalyst involves multiple phases. Generally, the catalyst is in the solid phase and the reactant and product are in the liquid phase or gaseous phase.
12.3 OIL EXTRACTION This study reviews the use of vegetable oil, produced on a small scale, as fuel. These are also called straight vegetable oils (SVOs), since they are filtered manually on a small-scale contrary to the advanced refining processes followed by the industries. SVOs are manufactured using simple technology, unlike the industrially manufactured oils. The chemical composition of SVOs differs from the industrially manufactured oils by the fact that SVOs have other minor compounds, for example, phospholipids, waxes, etc., which are present in little quantities or not at all present in the latter. SVOsare composed of 95% of triglycerides and 5% of free fatty acids and various impurities [28e31]. Extraction of oil from seeds involves several techniques like mechanical crushing, solvent extraction, cold pressing, microwave, etc., and extraction of oil from the seeds can be done through five different processes. Water-assisted, manual pressing, expelling, Ghanis, and solvent extraction are those five techniques generally used for the extraction of oil from the seeds [32]. In the waterassisted technique, there are two ways to extract the oil. In the first method, the finely ground oilseeds are mixed with water and heated to the boiling point of water; after a certain period, the oil that floats on the surface is skimmed off. In another method, powdered seeds are
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12.4 TRANSESTERIFICATION
mixed with water and squeezed to release the oil. Manual pressing is one of the general techniques which can be observed in our daily life. In the manual pressing technique, oilseeds are usually preground and are pressed in screw presses manually [33]. Expelling oil extraction technique consists of an expeller which is turning in a perforated cage with the help of an electric motor driven screw. The screw forces the material through a small outlet called as “choke.” High pressure is applied on the oilseed fed through the machine to haul out the oil. Expelling is a continuous method to extract oil continuously unlike manual pressing and water-assisted oil extraction which are batch systems. Ghani is the conventional way of extracting oil from seeds and still widely used in rural areas. In this, dried seeds are feed into the mortar, and it is crushed by rotating the mortar which is either powered by an animal or an electrical motor. The limitations of this method are the extracted oil requires further purification and yield is low compared to modern techniques. Solvent extraction is the widely accepted efficient method to extract oil on an industrial scale. In solvent extraction, oil is mixed with seed powder in a specific ratio, and the mixture is heated to the boiling point of the solvent. Finally, the pure oil is separated from the solvent-oil mixture by distilling the solvent in a rotary evaporator [34,35]. Mahua seeds are partially miscible in water, so it is difficult to extract oil through water-assisted technique, and manual pressing technique also yields less amount of oil per day. So, these two extraction techniques are inefficient and require a large amount of manpower to extract the oil from the seed. Weiss [36] used the cold method of extraction to extract castor oil by the standard method whereas Muzenda et al. [37] used the hot method of extraction to extract castor oil in a laboratory scale. Various extract methods are available for obtaining oil from seeds which are mechanical press, supercritical fluid extraction, and solvent extraction method. The mechanical method of extraction is the most widely used to extract oil from the seed. The turbidity of the oil produced with this method is usually high; it also contains a substantial amount of water and metal contents. Extraction using supercritical fluid generated very high purity oil but having a very high operating and investment cost is a disadvantage [38]. Solvent extraction is the best method to extract oil from seeds, which involves less cost and also gives more yield compared to other extraction techniques. Solvent extraction technique is that type of extraction technique in which seeds are crushed to a specified size for getting better yield and mixed with a solvent which can be separated by distillation [38]. A solution consists of solvent and solute which are chemically different (may be solid, liquid, or gas) in which solute gets dissolved
Storage
Cleaning
Milling, grinding
Oil expelling
Crude oil
Cake
Filtering
FIGURE 12.1
Outline of expelling extraction process.
in the solvent. Generally, solvents are liquids, but it can be in the gaseous state also. The amount of solute which is dissolved in a specific quantity of solvent varies with temperature. Water is considered as the universal solvent for polar molecules; complete proteins and ions are dissolved in water solvent in a cell. There are various applications for the use of a solvent such as in oil, gas, pharmaceutical and chemical industries, including in chemical syntheses and purification processes. Solvent extraction is a highly efficient technique whereas only economical at a larger scale. Usage of inflammable solvents results in the risk of safety and health issues. By considering all these factors and due to less complicity and for extracting more percentage of oil from the seeds generally researchers prefer expelling technique. Fresh seeds of mahua are collected, and then the plant materials are dried in the sun. Then the seeds are subjected to screw impeller mechanical press to extract the oil. Then the collected oil was filtered to remove the impurities and followed by water wash using distilled water. Then the pure oil was collected and then followed by raw oil characterization. The necessary steps involved in processing oilseeds by expeller are shown in Fig. 12.1.
12.4 TRANSESTERIFICATION Transesterification is the well-known chemical method to convert the triglycerides into methyl esters
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[39]. The oil extracted from vegetable source or animal fats are not suitable to unmodified diesel engine due to its high viscosity and acid value. These issues can be overcome by converting it into methyl esters which have similar fuel properties of diesel fuel [38]. Moreover, the cetane number of transesterified vegetable oil is quietly higher than diesel fuel which improves ignition quality of biodiesel in the engine. Catalyst
Triglycerides þ alcohol 5 Methylester þ Glycerol Meher et al. [40] stated that the best way to reduce the viscosity of the vegetable oil is to separate the glycerol molecules from three fatty acids. Mustafa Balat and Hawa Balat [41] gave an exhaustive review of biodiesel as a vehicular fuel. They gave a brief view about transesterification using different catalysts like alkali-based, acid and base catalysts, enzyme catalysts, and noncatalytic transesterification process for biodiesel production using different feedstocks. They also gave a review of the effect of reaction parameters like free fatty acid and moisture, molar ratio, alcohol type, reaction time and temperature, and catalyst on the reaction.
where A is the Arrhenius constant, R represents the universal gas constant (8.314 J/mol-K), T is the reaction temperature in K, Ea is the activation energy, and k stands for the rate constant. In this, the amount of catalyst used for transesterification process is assumed to be sufficient to move the reaction forward to produce the methyl esters, and reverse reaction is not taken into account. Moreover, catalyst concentration changes during the reverse reaction are assumed to be negligible. The second order kinetic model is given in Eq. (12.2). rA ¼
d½TG ¼ k1 ½TG ½ROH3 dt
where TG is the concentration of triglycerides, k1 is the rate constant, and ROH is the methanol. According to this Eq. (12.2), transesterification reaction follows the second-order kinetic model. However, the change in methanol concentration is constant due to high methanol to oil ratio for the reaction. Therefore, considering this excess amount of methanol, the overall transesterification reaction will tend to follow the first-order kinetic model as given in Eq. (12.3), rA ¼
12.5 CHEMICAL KINETICS OF BIODIESEL PRODUCTION FROM INEDIBLE SEEDS Temperature plays a vital role in the transesterification reaction. Hence, the chemical kinetic study is necessary to understand the influence of temperature on biodiesel conversion time [42]. The kinetic study was done to find the activation energy needed for the transesterification process. The minimum amount of energy required to shift the reaction toward the formation of products is known as activation energy which can be estimated from the relation between rate constant and reaction temperature [43]. The minimum energy required to start the product formation can be calculated from Arrhenius equation (12.1). The activation energy, Ea, is estimated from the slope of a plot between ln(k) and 1/T [44,45]. Currently, researchers absorbed the significance of chemical kinetics to estimate the specific activation energy for converting TG into biodiesel. Kinetics study on any reaction will generally provide information to find conversion percentage at a definite interval of time, the rate of conversion, and activation energy (Ea) for the reaction. The rate of methyl ester formation can be estimated by calculating the rate at which methyl ester is formed. k ¼ Ae
Ea RT
(12.1)
(12.2)
d½TG ¼ k1 ½TG dt
(12.3)
The initial boundary conditions for the transesterification reaction assumed as triglycerides concentration is zero at time t ¼ 0, and when the time reaches t it starts to decrease. Finally, the integration of Eq. (12.3) gives Eq. (12.4). ln½TG0 ln½TGt ¼ k t
(12.4)
½TG ¼ ln½TG0 ð1 XFAME Þ
(12.5)
Finally, integration rated form of conversion of methyl ester is obtained from Eq. (12.5) and given as Eq. (12.6) [46]. lnð1 XFAME Þ ¼ k t
(12.6)
12.6 PHYSICOCHEMICAL PROPERTIES OF SVOS The straight vegetable oil obtained from different feedstocks are having different physical and chemical properties. Hence, it is necessary to evaluate the physical and chemical properties of SVOs as per ASTM D6751 and EN14214 before utilizing it in a conventional diesel engine. SVOs quality mainly relies on its parent feedstock, time of harvest, storage conditions, and extraction methods [47].
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12.6 PHYSICOCHEMICAL PROPERTIES OF SVOS
12.6.1 Chemical characterization 12.6.1.1 Fatty acids The tendency of the fuel to burn appropriately is determined by the fatty acids present, whereas the combustibility of the fuel is determined by the degree of unsaturation of the fuel, which corresponds to the double and triple bonds present in the fatty acids. This degree of unsaturation of the fuel is proportional to the iodine value of the fuel, which is nothing but the number of milligrams of iodine consumed by 100 g of fat or oil. Fuel with low iodine value, that is, more saturated, is ideal for combustion. However, it should be noted that a very low iodine value is also not desired as it can lead to cold characteristics of the fuel. The classification of biodiesel is given in Table 12.1 [29]. The quality of combustion varies inversely with unsaturation, with the saturated fuels offering the highest quality of combustion. The presence of fatty acids in unsaturated oils can cause polymerization which can easily clog the rack actuator of the fuel injection system. On the opposite hand, saturated oils depict a higher viscosity at higher temperatures than their unsaturated counterparts [48]. 12.6.1.2 Phospholipid content During the mechanical oil extraction, there is a chance of phospholipids also being extracted from cellmembrane of seeds and kernel. The percentage of phospholipid varies with pressing force and filtration process. These lipids are undesirable content which are responsible for deposition of gums in the fuel tank and cause fouling in the valves and cylinder chamber. The concentration of phospholipids is getting reduced when seeds are cold-pressed at 50 C [49e51]. 12.6.1.3 Waxcontent Waxes are long-chain fatty acid esters and alcohols that can contain up to 46 carbon atoms. They originate from the shell and skin of specific seeds and fruit, respectively. The fraction of wax will vary depending upon the source of the seed, its ripeness, and the temperature at which oil is extracted. Waxes dissolve in the fuel at higher temperatures and hence should be filtered. During the combustion process, they do not hinder but TABLE 12.1
Classification of SVOs based on their iodine values.
Name
Iodine value
Examples
Saturated
5e50
Copra, palm-kernel oils
Monounsaturated
50e100
Groundnut, rapeseed, olive
Di-unsaturated
100e150
Sunflower, soybean, corn
Tri-unsaturated
>150
Flax, tung
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can cause blocking problems in the feed circuit, pump, and filter due to their high viscosity [51]. 12.6.1.4 Peroxide value This is used to determine the stability of the oil by evaluating its oxidation value. As it is obvious, the more the fuel is unsaturated, the more it is vulnerable to oxidation. Unsaturated fatty acids undergo fission, by splitting at the multiple bonds to give a series of short-chain compounds such as aldehydes and ketones which manifest themselves in the rancid odor of oils and fats. The rate of the reaction is slow initially but then increases exponentially. Van Grepen [52] showed that there exists a range of peroxide values for which cetane number increases linearly with the peroxide value.
12.6.2 Physical characteristics 12.6.2.1 Kinematic viscosity The viscosity of the neat vegetable oil is higher than that of the diesel fuels by 10e15 times at ambient temperature [53]. Viscosity is also observed to increase with increase in carbon chain lengths and unsaturation and decrease with rise in temperature. Viscosity can also be attributed to the high molar masses of the oils. The high viscosity of biodiesel decreases the injection flow which significantly reduces the pressure in the injection pump, filters, injectors, nozzles prompting poor atomization and vaporization. This issue makes the combustion incomplete [30,54,55]. Apart from that, viscosity dramatically affects the lubrication property. Some of the recent techniques to get over the difficulties faced by high viscosity are preheating, dual-fuelling, and mixing [51]. 12.6.2.2 Net calorific value This determines the heat given off per kg of combustion of the fuel. Although the value of absolute net calorific value (NCV) of SVOs is lower than that of diesel by 10%e15%, considering the high density of vegetable oils, the volumetric NCV of the SVOs is less than that of diesel fuels by 5%e6%. Forgiven unit power produced, this means 8% extra consumption of vegetable oil. NCV and density are the two parameters used to measure the volume flow rate of SVOs over diesel to inject the same power [51]. 12.6.2.3 Cetane number This signifies the time between the injection of the fuel and the start of its combustion. The higher cetane number of fuel indicates that the fuel is more flammable. The cetane numbers for vegetable oils are lower (29e43) than diesel (45e55). This produces difficulties in coldstarting and increased noise. At present, very few
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standard methods are only available to determine the vegetable oil and its biodiesel cetane number. Hence, there is a need to develop satisfactory analysis techniques to determine the viscosity of SVOs correctly [51]. 12.6.2.4 Density The density of SVOs is around 10% higher than the diesel fuels, and as mentioned above is a parameter used to determine the flow rates [51]. 12.6.2.5 Flashpoint Flashpoint is the minimum temperature at which the vapors from the oil get ignited when they are exposed to an external flame. In case of fuels, this acts as a safety parameter that determines its storage properties. The flash point of SVO is significantly higher than that of the diesel. Hence for these reasons, storage of diesel fuels needs extra precautions [51].
12.7 ALTERNATE FUELS IN COMPRESSION IGNITION ENGINES The compression ignition (CI) engine is currently the most efficient engine used for power generation and transportation. Also, its flexibility for different fuel and their blends makes it the most important type of engine for both automotive and power generation industries. Despite all these features of CI engine emission of greenhouse gases (GHG), NOx and particulate matter are the primary key factors leading to the search of new and more efficient ways to diminish emissions [56]. Many alternative fuels have given successful outcomes in the past, with both modified and nonmodified diesel engines [57]. The presence of certain unacceptable characteristics in the alternative fuels hinders its complete replacement of diesel fuels. Researchers have improvised upon the different admission techniques to maximize the fraction of alternative fuel that can substitute diesel [58]. Biodiesel consists of fatty acids and alkyl esters which can easily be used in compression ignition engine [59,60]. Its biodegradable and nontoxic nature derived from its biological origins make it even more attention-seeking [61]. It can also be termed as a cleaner fuel because of the absence of carcinogenic agents. Vast research has proved biodiesel to be an effective alternative to petrodiesel [62].
12.7.1 Application of unmodified vegetable oils in diesel engine 12.7.1.1 Use of neat vegetable oils in diesel engine A previous durability test on a diesel engine with mustard oil indicated that output power was decreased
as compared to diesel. Also, for mustard oil, CO emissions were higher at lower loads [63,64]. Coconut oil mixed with diesel in indirect injection diesel engine delivered higher brake power and net heat release rate, and diminished the amount of pollutants being discharged [65]. Long-term engine tests of palm oils and diesel mixes on a cutting-edge coordinate, direct injection diesel engine were performed. It was reported that the performance of engine smoke intensity and fuel consumption were found to vary marginally with running time [66]. Vegetable oils were used to run diesel engines directly, and some vegetable oils like karanja oil, rice bran oil, cottonseed oil, sunflower oil, jatropha oil, palm oil, etc., have been tested as fuels in diesel engines [67]. The literature review has indicated that, for short duration period, neat vegetable oils can give satisfactory performance in unmodified diesel engines. Also, it has been revealed that the complete substitution of vegetable oils has resulted in a slight decrease in maximum engine power and increase in fuel consumption compared to diesel fuel. A disadvantage of vegetable oils is its high viscosity resulting in poor atomization causing incomplete combustion [68]. This results in engine fouling due to carbon deposit on the injector and the valve seats. Another issue ruining routine utilization of common vegetable oils in present-day diesel engine is high sensitive viscosity, because of glycerine, which convolutes distribution (driving), sifting, and predominantly the exceptional atomization of the saturated fuel [69]. Vegetable oils are introduced as fuel for their substantial performance (emissions, efficiency, etc.), yet also to a specific number of issues experienced in their utilization. Such issues are often represented in writing: combustion chamber deposits, blocked filters, and various kinds of preparations are recommended: - mixing of vegetable oils in different percentages with diesel, - dual-fuelling or preheating vegetable oils, - employing exhaust gas recirculation (EGR), - combustion chamber modifications (injector, piston, etc.). The essential factor many times being emphasized via publications is that if vegetable oils are to be used efficaciously in a diesel engine, it is vital to have oil of good quality and also to make the integral adjustments to the engine [30,53]. 12.7.1.2 Use of neat vegetable oil blends in diesel engine Durability tests were conducted on direct injection, naturally aspirated, ford tractor three-cylinder diesel engine with sunflower oil and soybean oil. It was found
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that various amounts of vegetable oil with diesel fuel and different conditions of operation could provide different results on emissions and performance [70]. Research has also been done on the consequences of employing diesel-coconut oil blends and pure coconut oil on the emissions and performance of a diesel engine with direct injection. Increasing the quantity of coconut oil in the coconut oil-diesel blends hasresulted in lower smoke and NOx emissions. They also reported that the fuel consumption (BSFC) was increased due to the lower calorific value of neat coconut oil fuel compared to diesel fuel. The spray pattern of coconut oil and the blend with diesel was also analyzed at different temperatures and that due to the lower calorific value of coconut oil, the heat release patterns showed lower spikes with reduced premixed combustion [71]. Experiments on a DI-CI engine using degummed Jatropha curcas oil (with an objective of avoiding many problems such as injector coking, high exhaust gas emission, and effect to the engine components) were conducted and combustion and emission characteristics of CI engine were reported. It was reported that 10% degummed J. curcas oil (DJO10) blend gives better combustion compared to 10% J. curcas oil (JO10) and the efficiency of both fuels were closer to diesel. It was also reported that HC, CO of JO10, DJO10 are higher than diesel fuel. NOx emission of JO10 is increased by 9.38% and for DJO10 decreased by 0.44% compared to diesel fuel. Smoke emission is reported to be less [72]. The performance of vegetable oils in a four-stroke, single-cylinder, stationary diesel engine was examined. The linseed oil, mahua oil, rice bran oil, and ester of linseed oil were blended with diesel at different proportions and tests were conducted. It is reported that the performance of vegetable oils is near to that of diesel and could be used for agricultural purposes [73]. Experimental investigation on a direct injection CI engine at constant speed and evaluated performance, emission, and combustion behavior of blended jatrophaoil under unheated environments were performed. It was concluded from the results that jatropha blends 20% or less were found to be promising alternative fuels. They could be directly used in CI engines without any major modifications in the engine [74]. The difficulty of low volatility, polyunsaturated characters, and high viscosity can be altered by blending of diesel with vegetable oils and henceforth resolve the difficulties of operation of the diesel engine with pure vegetable oil [75]. It is noticed that without any modification a diesel engine would successfully run on a blend of 80% diesel with 20% of vegetable oil without any damage to the parts of the engine. Refined pure vegetable oils cannot be directly used in diesel engines with directinjection [76],when such engines bring up to half of their theoretical power and have a mean chamber
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temperature less than 200 C. Though, the flash point of vegetable oil is more than diesel oil: 93 C for diesel oil as contrasting to 240 C for jatropha oil. It means that few of the oildroplets will not be evaporated; instead they will stick to the walls, ensuing in deposits of tar. Shortly after such deposits accumulate on the nose of the injector, there will be trouble in spraying and then the operation worsens. Also, they enter in top ring of the piston throat, restraining workability and result in clogging and quick wear of the ring [51]. Direct-injection diesel engines are most widely used to generate shaft power and current, and in rural applications, it appears more appropriate to examine their operation with SVO as a fuel. Still, such engines create complications when vegetable oil is employed.
12.7.2 Use of biodiesel and its blends The performance, emissions, and combustion characteristics of a diesel engine fuelled with biodiesel, without any engine modification, were carried out by a different researcher. It was found that at maximum load conditions the specific fuel consumption of biodiesel is more by 17% that of diesel. The brake thermal efficiency with diesel is 25.9% and decreased to 24.5% with biodiesel [77]. Overall combustion characteristics of biodiesel and its blends are found to be quite similar to diesel. Brake-specific fuel consumption (BSFC) is the ratio of the mass of fuel consumed by the brake effective power generated in an engine. BSFC is inversely related to thermal efficiency. Increase in BSFC is accredited to enhancement of oxygen from the fuel and not from the intake of air. Almost all investigators have described an increase in BSFC when using biodiesel blends and biodiesel. When using biodiesel, most of the scientists have seen a substantial variation in thermal efficiency [78,79]. Torque, brake power, SFC, and brake thermal efficiency were found comparable to that of the dieselfuelled engine when esterified palm oil was used as a fuel for CI engine [80]. The calorific value of petroleum diesel is approximately 5% more than the calorific value of cottonseed oil (CSO) biodiesel. The torque and power was hence reduced because of lesser calorific value [81]. The experiment was carried out by Pongamia glabra, rice bran oil, palm oil, rapeseed oil, and neem oil for an alternate fuel for diesel engine. The results of the tests were discussed concerning the performance and combustion parameters like delay period. These results indicated that the vegetable oils and their methyl esters performed with acceptable thermal efficiencies as fuels for diesel engines. Methyl esters of vegetable oils had shorter ignition delays and longer combustion duration than diesel oil due to their higher viscosity [82]. The atomization of fuel was affected by higher viscosity and surface tension of the fuel. The coconut oil methyl ester
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had got the smallest mean drop size when compared to peanut and canola methyl esters due to its lower surface tension. This reduction in fuel drop size improves the combustion efficiency of the fuel. The fuel atomization is affected by surface tension. The biodiesel with higher surface tension offers resistance to fuel atomization [83]. The bulk modulus is an important parameter for the combustion analysis; it is a measure of resistance to compressibility. Bulk modulus decreases with increase in temperature and increases with increase in pressure. The vegetable oil esters are less compressible than diesel. This less compressibility leads to increased mass delivery of the fuel. The high value of bulk modulus causes an advance in injection timing which leads to more fuel accumulation in the combustion chamber. It was reported that the bulk modulus is higher for unsaturated methyl esters and increases with the chain length of the acid [84]. Therefore, a quicker transmission of the pressure wave is received by the nozzle commencing injection pump, hence the elevated needle in advance. It also leads to an earlier injection of biodiesel at elevated pressures and same crank angle in the combustion chamber. The quantity of the fuel at an early stage of premixed combustion rises because of increase in injection pressure [85]. It has been found from most of the research work that biodiesel fueled engines emit more NO than diesel. Generally, NOx formation is influenced by the exhaust gas temperature (EGT). The NOx formation is dependent on the temperature inside the cylinder and the NOx formation reaction requires high activated energy. Higher temperature would convert the atmospheric nitrogen into NOx [86]. The presence of carbon in biodiesel molecule has a biological nature. Each rapeseed oil methyl ester (RME) molecule comprises about 94.73% organic carbons whereas in the case of rapeseed oil ethyl ester (REE) molecules the biological carbon is almost 100%. This biological carbon increases the exhaust gas temperature by about 5 C in the biodiesel blend and this is another reason for the increase in NOx [87]. The viscosity of the fuel is also one of the reasons for NOx formation in CI engine. The fuel viscosity affects the fuel injection characteristics and fuel atomization. The increase in viscosity leads to an increase in biodiesel fuel injection by mass. The disadvantages of having a higher viscosity of biodiesel are as follows: increased spray jet penetration, lower spray cone angles, and bigger droplet sizes also result in poor atomization. Early start of injection along with lower spray cone angles is the primary cause for lesser thermal efficiency and increased NOx emissions of biodiesel [88]. Iodine number is another parameter influencing the NOx formation in CI engine. Biodiesel blends with high iodine number and low iodine number fuels could support reducing and increase in NOx, respectively. The
animal-based biodiesel has a lower iodine number than those for rapeseed- or soy-based biodiesel. Also, lowering the aromatic content in the animal-based biodiesel could help in reducing NOx emission [89]. Organic compounds consisting of a peroxide group bonded to two tert-butyl groups and compounds like ethylhexyl nitrate are cetane improvement additives that may also be helpful for NOx reduction [90]. Increase in unsaturated fatty acid reduced the cetane number and increased the iodine value. The increase in saturated fatty acid content increased higher heating values [91]. The most common fatty esters contained in biodiesel are mainly C12 to C16 fatty acids including lauric acid (C12:0), myristic acid (C14:0), palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2), and linolenic acid (C18:3). Emission tests were conducted in a CI engine and observed that there was a decrease in NOx emissions with saturated fatty acids like lauric acid and palmitic acid and increase in emissions with unsaturated fatty acids like linoleic acid [92]. The formation of smoke happens primarily in the cylinder at fuel-rich zone, high pressure, and low temperature. Formation of smoke can be governed by the availability of oxygen decreases overrich regions (it is the region where the fuel is more than needed, i.e., more than the desired fuel-air ratio) [93]. When the engine runs at full open throttle on underload, all of the fuel is injected to give maximal power, which is a rich mixture. Therefore, at higher load, fuel-air ratio increases, fuel is injected in huge amounts, and most of the fuel which is unburnt escapes with the exhaust ensuing in increased emissions of smoke. Formation of smoke was less under the load condition less than 75%, and it increases with the increase in load [94]. The CO generated in the clean diesel fuel could be reduced by 24% if 30% of biodiesel is blended with it. This is because biodiesel contains higher oxygen content compared to the conventional fuel to enhance the complete combustion [93]. The CO2 released by burning biodiesel would not harm the environment, and it does not contribute to the greenhouse gas formation. The reason behind this is because biodiesel is produced from the crops which use the already available CO2 which is present in the atmosphere. However, in the case of the commercial petroleum diesel, the CO2 released are from the deposited carbon inside the earth’s crust which contributes to the greenhouse gas effects [95]. The maximum thermal efficiency and preferable reduction of engine emission were attained in 20% biodiesel blend. So, it was found to be optimum condition for linseed oil methyl ester (LOME) that improved the thermal efficiency of the engine by 2.5%, reduced the exhaust emissions, and the specific energy consumption was higher; and there was the reduction in exhaust smoke levels. Exhaust temperatures were increased
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due to a higher percentage of LOME which led to a 5% increase in NOx. The experimentation verified that self-lubricity of LOME in biodiesel contributed to engine performance significantly. The additional lubricity provided by B20 demonstrated comparable power and torque as generated by the combustion of commercial petroleum fuels [96].
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Due to stringent emission norms, most automobile manufacturers are downsizing engines and supercharging them to produce the required power and torque, while increasing overall efficiency. Butin the near future it will be required to resort to renewable fuels to run our engines, as fossil fuels are getting depleted. The easiest way to move on is by modifying existing engines to run on renewable fuels [97].
engines. Many authors have investigated the effectiveness of this method and suggest that increasing the intake air pressure is achieved either through turbocharging or supercharging. Al Hinti et al. [102] boost up the suction air pressure could increase air density and improve the volumetric efficiency of engines during each cycle. Generally lower end engine, the suction air pressure was increased in between to 0.2 and 0.8 bar. The output power of engine varies on the value of suction pressure increase and the engine geometrical and operational condition. As mentioned earlier, forced intake has been identified as one of the most promising engine modification to meet increasingly strict emission standards without compromising on the power, performance, and efficiency of the IC engine. This concept could be effectively put to use in making biodiesel a more prominent and promising alternative for diesel in CI engines.
12.7.3.1 Forced intake air pressure The phenomenon of forced intake can be defined as supplying air to the engine at a higher pressure than 1 atmosphere. By doing so, we are forcing air into the cylinder during suction stroke in addition to the sucking action of the air by the engine. This increased pressure will induce some amount of pumping loss in the compression stroke, but the benefits of forced intake outweigh its drawbacks. As per the universal gas law, with an increase in intake pressure for the same swept volume, the mass of air forced into the cylinder increases [98]. This increased intake air mass helps improve combustion and produce cleaner emissions. The cause of the same can be explained by the simple heat transfer law H ¼ mCpDT. Assuming that the coefficient of heat transfer remains constant (almost) for a certain amount of heat, the increased mass will lead to a reduction in DT. Hence, the forced intake pressure method reduces the in-cylinder temperature compared to a naturally aspirated engine by providing the same amount of fuel [99]. As NOx production is a function of temperature, the same is expected to reduce significantly after pressurizing the intake air. Improvement in fuel economy is also expected when forced intake phenomenon is applied [100]. Karabektas [101] studied the effects of a turbocharger on a diesel engine with biodiesel as fuel. BSFC was increased for biodiesel due to lower calorific value and higher density of biodiesel. Smoke emission decreased for turbocharged engine and NOx emission was increased due to better combustion. However overall performance of the turbocharged engine improved when compared to the naturally aspirated engine. Increase in the suction pressure of air is an effective approach to improve the efficiency and power of IC
12.7.3.2 Fuel modification Addition of dimethyl carbonate to mahua oil biodiesel by 5%, 10%, 15%, and 20% reduces the NOx emissions. The increase in additives reduced the NOx emissions by 40% and improves the thermal efficiency by 5%. HC and carbon monoxide emissions reduced marginally with an increase in an additive to mahua oil biodiesel [103]. Blending with another fuel with better cold flow properties is inevitable. More researches are performed by adding alcohol as an additive with biodiesel to improve cold flow properties, and a few types of research involved the oxygenated diethyl ether addition at a lower volume comparatively. Such changes in fuel improved cold flow properties and also resulted in better combustion and reduced emission characteristics. It also includes the blending of diethyl ether with biodiesel which improves the cold flow properties and cetane index [104]. Pyrolytic distillation methods are used for producing diesellike fuel (DLF). During the test, it is observed that the distillation temperature of the DLF was close to a typical diesel fuel sample. Hence, The DLF can be used in CI engine fuel. The DLF has an advantage of increases the engine torque, brake thermal efficiency, brake mean effective pressure, and decreases specific fuel consumption of the engine for the rated loaded condition [105]. Compared to CaO and trisodium phosphate, tripotassium phosphate shows high catalytic action during transesterification reaction [106]. About 97.3% fatty acid methyl ester (FAME) yield wasobtained with a catalyst concentration of 4 wt% at 60 C for 120 min. In addition to this, used regenerated catalyst with aqueous KOH solution for transesterification obtained FAME yield of 88%. Mixing of cosolvent converted the reaction state from three-phase to two-phase but decreased the FAME yield which is exact opposite of
12.7.3 Engine and fuel modification
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homogeneous catalysts. In the presence of cosolvents for reducing the catalytic activity the catalyst particles were agglomerated by the glycerol drops. 12.7.3.3 Engine modification On the basis of earlier research, it was identified that the engines running on the biodiesel emit lower CO, unburned HC, and PM compared to emissions from diesel; it was observed that there was a small rise in NO emissions. Further reduction in emission can be achieved by either use of a modification of engine operating parameters, fuel additives, or after-treatment techniques [107]. Among these methods, after-treatment techniques like diesel particulate filter (DPF) has become more popular as it controls the particulate matter which comprises mainly of carbonaceous soot particles that cause a severe hazardous effect on the environment [108]. The blending of jatropha oil and diesel in the low heat rejection diesel engine (L.H.R) improves the performance compared to raw jatropha operation. Combustion duration and ignition delay also reduces with blending of jatropha oil and diesel. A substantial amount of this waste heat can be recovered by applying a thermal barrier coating (TBC) on the cylinder liner, piston crown, cylinder head, and exhaust valve. It reduces the heat loss due to conduction and keeps the outer surface temperature lower which eliminates the necessity of water circulation for cooling. Also, the average in-cylinder temperature increases which results in combustion of charged particles trapped in the crevices which do not take part in combustion due to low temperature. Thus, improvement in the combustion of fuels leads to higher efficiency [109]. Increasing the jatropha fuel injection pressure from 200 to 240 bar increases the brake thermal efficiency and decreases the smoke emission [110]. Advancement of injection timing is required for blends of biodiesel and ethanol with diesel due to the displacement of 50% diesel by the blends. The results revealed that advancing start of injection led to earlier combustion. Advance injection timing doubled the NOx emissions and reduces the smoke emission by 60%e70% for all the blends. Due to earlier combustion increase in cylinder pressure, temperature, and NOx emission was observed. The carbon monoxide emission reduces with advancing the injection timing significantly at lower loads [111]. Preheating of biodiesel also significantly increases the efficiency and reduces the emissions. But NOx increases due to the presence of unsaturated fatty acids and the advanced injection caused by the higher density of jatropha biodiesel [112,113].
12.8 ENGINE EXHAUST EMISSIONS The diesel engine has become a preferred prime mover among the various kinds of internal combustion
engines because of its higher thermal efficiency and lower fuel consumption. This includes heavy trucks, buses, industrial power generation equipment, offhighway construction, and mining equipment [114]. Emissions from diesel engines including carbon monoxide (CO), carbon dioxide (CO2), nitric oxide (NO),unburned hydrocarbon (HC), sulfur oxide (SOx), nitrogen oxide (NOx), and particulate matter (PM) lead to severe respiratory disorders. Reduction in CO is generally accompanied by an increase in CO2 [115]. Total hydrocarbons are waste fuels which could not be combusted, and so the presence of the same is an indication that engine is not running at full efficiency. Oxides of nitrogen and sulfur are more hazardous in comparison to the emission above products and contribute to depletion of ozone layer. So, stricter emissions standards are being implemented keeping in mind the deteriorating health of Mother Earth [116]. In the past two decades, many types of research have been conducted to control the emissions. Various parameters were taken into account, which included engine design modification, exhaust after treatment,fuel modification, etc. Smith [117] inscribed, “Hence we summarize, as others have done, that formation of soot is essential in the operation of compression ignition engines.” This was the most common opinion at earlier times but later, following experiments have verified that emissions such as soot can be limited in engine cylinder itself, as revealed by Tree et al. [118]. Among the listed methods, after-treatment techniques like diesel particulate filter (DPF) have become more popular as they block the particulate matter which comprises mainly of carbonaceous soot particles that cause a severe hazardous effect on the environment and respiratory system [119].
12.8.1 Formations of emissions The United States Environmental Protection Agency released a technical report regarding nitrogen oxide. NOx specifies a family of seven compounds. Nitrogen dioxide (NO2) is a leading air pollutant, and as well it reacts with the surroundings to form acid rain and ozone (O3). It is significant to know that the ozone that we need to reduce is ozone present in the troposphere; especially, ozone in the atmospheric air that we inhale [120]. The family of NOx compounds and their properties are listed in Table 12.2. NOx emissions from combustion are mainly in the form of NO. According to the Zeldovich equations, NO is produced at temperatures above 1300 C and due to the amount of oxygen available (about 200,000 ppm) in the atmosphere. At temperatures less than 760 C, nitric oxide is either produced in minor concentrations or not even a trace. NO is formed as a function of air to fuel ratio and is further noticeable when the
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
12.9 EXPERIMENTAL METHODOLOGY
TABLE 12.2
Family of NOx compounds and their properties [120].
Formula
Name
Nitrogen valence
N2O
Nitrogen oxide
1
NO N2O2
Nitric oxide 2 Dinitrogen dioxide
Colorless gas, slightly water soluble
N2O3
Dinitrogen trioxide
Black solid, water soluble, decomposes in water
NO2 N2O4
Nitrogen dioxide 4 Dinitrogen tetroxide
Red-brown gas, very soluble in water, decomposes in water
N2O5
Dinitrogen pentoxide
White solid, very soluble in water, decomposes in water
3
5
Properties Colorless gas, water soluble
mixtures are on the lean side of the stoichiometric ratio of 50 [121]. The Zeldovich equations are [120]: N2 þ O /NO þ N
(12.7)
N þ O2 /NO þ O
(12.8)
N þ OH /ON þ H
(12.9)
Emissions of hydrocarbon generated from the existence of partially burned or unburned fuel in the exhaust of the engine. HC emissions are various compounds of hydrogen, carbon, and sometimes oxygen. Emissions of HC result in the formation of ozone, which causes eye irritation and produces photochemical smog. Though, some of the exhaust hydrocarbons are not found in the fuel but are hydrocarbons resulting from the fuel whose composition was altered due to a chemical reaction that did not go to termination. For instance: formaldehyde, 1,3, acetaldehyde, benzene, and butadiene, all are classified as harmful emissions [122]. CO generation is well recognized. The conditions at which there is no sufficient oxygen required for complete oxidation and some of the carbon in the fuel turns out to be CO. The proportion of CO, for C/H ratios and a fuel composition range, is a function of the relative airfuel ratio. Even in a situation in which enough oxygen is present, dissociation can occurby high-peak temperatures. In combustion chemical reactions water vapor and carbon dioxide separate into CO, H2, and O2. The chemical reaction governs the transformation of CO to CO2. CO þ OH 4CO2 þ H
(12.10)
The exhaust gases are passed through the filter to separate particulate matter (PM) which consists of soot and other liquids, as well as solid materials. Generally, the particulate matter is separated into dry fractions or
303
a soluble or insoluble fraction. The insoluble fractions are responsible for determining the soot percentage in the exhaust gases after filtration. Often the diesel exhaust consists of an insoluble fraction with approximately half of the soot contents in it. The other half of the insoluble fraction consists of water vapor, unburnt oil or fuel, wear metals and sulfate compounds generated during combustion [123,124]. The advancement of hydrocarbons presents in liquid or vapor phase to get converted into solid soot particles and feasibly again to gas phase products comprise of six different ordinarily known processes which are in the order as follows: pyrolysis, nucleation, coalescence, surface growth, agglomeration, and oxidation. The last process is oxidation where hydrocarbons get converted into CO, CO2, and H2O throughout the process. All the processes mentioned above occur separately may be in different space constraints or time constraints such as in laminar diffusion flames [125].
12.9 EXPERIMENTAL METHODOLOGY 12.9.1 Solvent-assisted oil extraction Mahua seeds were collected from in and around Trichy areas. Collected seeds were dried in sunlight to get rid of moisture and maximize the oil yield. The dried seeds were crushed into a particle size of 1 mm. Oil extraction was carried out in a 500 mL single neck round bottom flask with 1:5 ratio of seed to solvent. The process temperature was maintained at 40 C with the help of water bath. After 1 h of extraction time, the solvent-oil mixture was taken into the rotary evaporator to separate the oil and solvent.
12.9.2 Biodiesel synthesis Free fatty acid value is the deciding factor to produce biodiesel whether by undergoing single or two-step transesterifications. The FFA of mahua oil is found to be 25 mg KOH/g of an oil which is far high than limits. In this condition, it is not advisable to use base catalyst because of soap formation during the transesterification process. Hence, two-step transesterification process was taken to produce biodiesel. In the first step, acid catalyzed transesterification was performed to reduce the FFA to less than 1 mm KOH/g of oil. Then basecatalyzed transesterification was carried out. 12.9.2.1 Esterification The esterification process was performed on a hot plate which is equipped with reflux condenser, magnetic stirrer, and temperature controller. Mahua oil is initially heated at 60 C for an hour to evaporate the moisture.
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12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
After that 1:6 ratio of methanol and 2 wt% of sulfuric acid were added one by one to the oil. Then the esterification was carried out for 30 min on a hot plate with electrical power of 350 W at 55 C. After completion of the esterification process, the mixture is shifted to separating funnel and kept for 2 h to form two distinct layers. In these two layers, top layer consists of excess methanol, impurities catalyst and bottom layer contain esterified Mahua oil. The acid value of esterified Mahua oil is determined by titration method which is found to 0.8 mg KOH/g of oil. 12.9.2.2 Design of experiments Optimization of CH3ONa catalyzed transesterification was performed using the design of experiment tool. For this Design Expert 10.0 software used to design the transesterification experiments. Response Surface Methodology (RSM) method was chosen to optimize the process parameters such as temperature, catalyst concentration, molar ratio, and reaction time and study the effect of these parameters on biodiesel yield. Table 12.3 presents the parameter range and levels of independent variables for biodiesel production. 12.9.2.3 Transesterification The detailed photographic view and the experimental biodiesel setup is shown in Fig. 12.2, and the transesterification processes use a three-neck round-bottomed flask having a capacity of 500 mL batch reactor. Methanol with 99.9% purity was used for transesterification. The apparatus was employed with Remi adjustable speed DC motor, a Liebig condenser, k-type thermocouple with a thermometer pocket, a mechanical kneader along with a tachometer, and a stopper for sample removal. The reaction temperature was maintained with the help of a constant temperature heating mantle with 0.1 C accuracy. The transesterification reaction was performed with methanol to oil ratios (3:1, 6:1, 9:1, 12:1, 16:1), 0.5%, 0.88%, 1.25%, 1.63%, 2% by weight of catalyst and the reaction was carried at temperatures 40, 45, 50, 55, 60 C and the reaction times were 60, 90, 120, 150, and TABLE 12.3
Input parameters for biodiesel production.
180 min, respectively. The esterified oil was preheated for half an hour at 60 C. After the oil reached the desired temperature, the methanol and catalyst were mixed according to the trial condition. After accomplishment of the reaction, the product was allowed to settle in a separating funnel for minimum 24 h. Finally, the glycerol was removed from the bottom of the separating funnel to get mahua biodiesel from the top of the funnel. Then the biodiesel was subjected to water wash. In this process, distilled water is taken such that the quantity of water taken must be more than double the amount of oil. Then the distilled water was heated up to 50 C. Then this warm water and biodiesel are mixed in a flask and stirred thoroughly and kept in a separating flask for 30 min so that the sediments, excess alcohol, and other impurities were separated from the biodiesel. Then the water is removed from the flask, and the remaining oil was heated up to 70 C, to get the biodiesel which was a clear yellow liquid. 12.9.2.4 Biodiesel optimization In this research, studies on optimization of methyl ester yield are carried. The most critical factors affecting the yield of the biodiesel production are molar ratio, catalyst concentration, reaction temperature, reaction time, and stirrer speed. In order to study the combined effects of all the above-discussed parameters, simulation tools (RSM tool in DoE software) are used. The optimized results, that is, trials which are obtained from DoE software are utilized practically for production of biodiesel from inedible source, using methanol (CH3OH) like alcohol, sodium methoxide (CH3ONa) as a catalyst. Design of Experiment (DoE) software has given 32 experiments to optimize the transesterification process. Those trials were conducted, and the maximum yield for biodiesel was found out to be 95.4%. The results have been tabulated for each trial in Table 12.4. Out of the 32 optimal trials conducted for the production of biodiesel, a trial with 1:9 M ratio, 1.25% catalyst, 52.5 C temperature for 120 min and 800 rpm stirrer speed has given the maximum yield. Mass production of biodiesel is now done in this optimized condition. Fig. 12.3 shows biodiesel production process for different trials. 12.9.2.5 Evaluation of the model and analysis for a variance for biodiesel
Range and level Independent variables
L2
L1
0
D1
D2
Temperature ( C)
40
45
50
55
60
Reaction time (min)
60
90
120
150
180
Molar ratio (methanol:oil)
3:1
6:1
9:1
12:1
16:1
Catalyst concentration (wt%)
0.5
0.88
1.25
1.63
2
Stirrer speed (rpm)
600
700
800
900
1000
From the ANOVA results of transesterification process it is evident that the linear terms A, B, C, D; quadratic terms A2, B2, C2, E2; and interaction terms AB, AC, AD, BC, BD, CE, DE are significant terms to affect the biodiesel conversion. The ANOVA response for the transesterification process ispresented in Table 12.5. The principle model analysis was based on the analyzing of variance, which provides the numerical
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
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12.9 EXPERIMENTAL METHODOLOGY
1
2
45 5
1
3
6
Water out
2
4 Water in
4 7
3
5 6 8
7 8
1. Temperature controller
5. Stirrer rod
2. Motor
6. Thermocouple
3. Condenser
7. Three neck round bottom (RB) flask
4. Motor Stand
8. Heating mantle
FIGURE 12.2 Schematic and photographic view of transesterification setup.
information for the “P-value.” The statistical analysis of the response parameter (yield of inedible oil-ME) is shown in Table 12.5. It was observed that the model is significant due to “P” value lower than .0001 (reference limit of “P” value was chosen as .05). The regression analysis gave a quadratic model which is given below Yield ¼ 49:35 þ 2:53A 13:77B þ 9:84C 4:67D 0:67E 0:87AB þ 9:50AC þ 4:37AD 3:50AE þ 9:37BC 5:50BD þ 3:88BE þ 0:63CD þ 9:75CE þ 2:87DE þ 1:67A2 þ 4:76B2 5:10C2 þ 1:51D2 þ 3:13E2 (12.11) 2
The goodness of estimation (changeable R ) and the statistical regression fit (determination coefficient-R2) were computed as 0.9247 and 0.975, correspondingly. The changeable R2 value refers to the number of prognosticators in the model, and R2 value specifies the total response variability later considering the significant factor. Together they specify whether the models fit well or not. Adjusted R2 and R2 value postulated that the accessibility of the model and accuracy were fair that roots the response plots study with the model was feasible. Several chemical and physical properties for the biodiesel characterization were determined. The properties consist of density, fire and flash point temperatures, pour and cloud point temperatures, kinematic viscosity, acid value, carbon residue, copper strip corrosion, and calorific value.
12.9.2.6 Experimental procedure for kinetics study Mahua oil was made to react with methanol using the homogeneous catalyst (CH3ONa). The trial condition used is temperature 45, 50, and 55 C, oil to alcohol ratio of 1:9 for 120 min using 1.25 wt% of the catalyst. At a time, the interval of 24, 48, 72, 96, and 120 min, 2 mL of samples were taken out and sent for 1H-NMR spectrum analysis. Methyl ester formed during each time interval is obtained making use of the NMR chart. In NMR spectrum, the formation of methyl ester and excess methanol are indicated at 3.6 and 3.5 ppm, respectively. The unconverted triglycerides that are protons of CH2 groups are present at 2.3 ppm. The percentage of conversion of methyl ester is calculated using following Eq. (12.12). C ¼ 100
ð2 XÞ ð3 YÞ
(12.12)
where C ¼ Conversion of triglyceride to methyl ester, X ¼ Integration value of the protons of the methyl esters from NMR chart Y ¼ Integration value of the methylene protons NMR chart Amount of methanol is calculated making use of the formula given in the following equation Amount of methanol ¼
The volume of methanol Density of methanol Molar mass of methanol
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
TABLE 12.4
Biodiesel yield for all the 32 trials obtained from design of experiment. Temperature ( C)
Catalyst (wt%)
Reaction time (min)
Stirrer speed (rpm)
Predicted yield (%)
Experimental yield (%)
1
12
56
1.63
150
900
77.61
68.70
2
9
52
1.25
120
800
48.75
39.65
3
9
52
1.25
120
800
48.75
60.21
4
12
56
1.63
90
700
74.55
72.00
5
6
56
1.63
150
700
11.22
9.00
6
9
52
1.25
120
1000
62.41
72.12
7
16
52
1.25
120
800
68.84
79.78
8
12
48
0.88
90
700
78.36
80.00
9
6
48
0.88
90
900
59.15
61.40
10
9
52
2.00
120
800
45.41
50.70
11
6
48
1.63
90
700
46.32
50.78
12
9
52
1.25
120
600
64.44
62.00
13
12
48
1.63
150
700
92.63
90.12
14
6
48
0.88
150
900
66.89
65.00
15
6
56
0.88
150
900
9.43
5.00
16
9
52
0.50
120
800
3.01
5.00
17
6
56
0.88
90
700
54.08
56.00
18
9
52
1.25
120
800
48.75
50.00
19
6
56
1.63
90
900
83.95
82.01
20
9
52
1.25
120
800
48.75
46.90
21
3
52
1.25
120
800
50.57
46.90
22
12
48
0.88
150
900
54.72
50.00
23
9
52
1.25
120
800
48.75
40.60
24
12
56
0.88
150
700
14.18
9.43
25
6
48
0.88
150
700
78.03
80.00
26
12
48
1.63
90
900
77.23
75.00
27
9
52
1.25
60
800
62.80
59.80
28
9
52
1.25
120
800
48.75
47.90
29
9
52
1.25
180
800
42.50
52.78
30
9
45
1.25
120
800
98.49
95.40
31
9
60
1.25
120
800
44.63
55.00
32
12
56
0.88
90
900
12.57
7.80
12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
Molar ratio (methanol:oil)
306
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
Trial No
307
12.9 EXPERIMENTAL METHODOLOGY
Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Trial 6
Trial 7
Trial 8
Trial 9
Trial 10
Trial 11
Trial 12
Trial 13
Trial 14
Trial 15
Trial 18
Trial 19
Trial 20
Trial 16
Trial 17
Trial 21
Trial 22
Trial 23
Trial 24
Trial 26
Trial 27
Trial 28
Trial 29
Trial 31
Trial 25
Trial 30
Trial 32
FIGURE 12.3 Photographic views of biodiesel yield obtained from 32 trials.
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12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
TABLE 12.5
ANOVA table from design of experiment.
Source
Sum of squares
DF
Mean square
F-value
p-value Prob > F
Model
17954.21
20
897.71
9.7
0.0002
A-temperature
500.6894
1
500.69
5.41
0.0402
B-time
4351.349
1
4351.35
47.01
<0.0001
C-catalyst
2696.216
1
2696.22
29.13
0.0002
D-molar ratio
617.932
1
617.93
6.68
0.0254
Espeed
6.18135
1
6.18
0.067
0.8008
AB
64.08002
1
64.08
0.69
0.4231
AC
1486.103
1
1486.1
16.06
0.0021
AD
348.1956
1
348.2
3.76
0.0785
AE
286.2864
1
286.29
3.09
0.1064
BC
1295.64
1
1295.64
14
0.0033
BD
1289.169
1
1289.17
13.93
0.0033
BE
277.056
1
277.06
2.99
0.1115
CD
11.9025
1
11.9
0.13
0.7267
CE
1807.1
1
1807.1
19.52
0.001
DE
66.9124
1
66.91
0.72
0.4133
A2
219.9673
1
219.97
2.38
0.1514
2
954.1803
1
954.18
10.31
0.0083
2
1103.727
1
1103.73
11.93
0.0054
2
27.93702
1
27.94
0.3
0.5937
2
E
394.7453
1
394.75
4.26
0.0633
Residual
1018.11
11
92.56
Lack of fit
740.5743
6
123.43
2.22
0.1992
Pure error
277.5353
5
55.51
Cor total
18972.32
31
B
C
D
The total concentration of methanol is obtained using the following equation The total concentration of methanol ¼
Amount of methanol The volume of methanol þ Volume of Mahua oil
The concentration of methyl ester is calculated making use of the formula given in the following equation
The concentration of ester ¼
Significant
Not significant
Once the concentration of methyl ester is found from NMR result, a kinetic plot is plotted with time in X-axis and concentration of methyl ester in Y-axis. Linear regression analysis is made use to plot the line between time and methyl ester concentration. The slope of the given line gives the initial methyl ester rate concerning the corresponding reaction temperature. Kinetic analysis is conducted for transesterification reaction at 45, 50, and 55 C. Once the initial methyl ester rate is
The methyl ester signal value Total concentration of methanol Methyl ester signal value þ Methanol signal value
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12.10 RESULTS AND DISCUSSION
obtained for the corresponding reaction temperatures, an Arrhenius plot to find out the activation energy needed for conversion of triglyceride to Fatty Acid Methyl Ester (FAME) or biodiesel is made. Arrhenius plot consists of reciprocal of temperature in the X-axis and the natural logarithm of initial methyl ester rate in the Y-axis.
12.10 RESULTS AND DISCUSSION 12.10.1 Comparision of predicted yield and actual yield The predicted and actual value is shown in Fig. 12.4, and the adjusted R2 value was 0.9294 which denotes 92.94% of the variability. The predicted value and the actual values are reasonably very close to each other and that values are approaching unity. This indicates that the data fit with the model and convincingly good estimate of response for this system. Also, the residuals also validate the corrected model. Residual is a difference between actual and theoretical responses.
12.10.2 Effect of process parameters on biodiesel yield This section describes the interaction effect of transesterification process parameters namely methanol to oil ratio, that is, molar ratio, the catalyst concentration in % w/w, reaction temperature, reaction time, and stirring speed on biodiesel yield. Figs. 12.5e12.14 show the interaction effects of these parameters on biodiesel yield and the same is discussed below.
Fig. 12.5 indicates the graph is drawn to show the effect of molar ratio and temperature on the yield and the maximum yield obtained at a molar ratio of 9:1 and at a temperature of 52.5 C. From the graph, it is observed that yield increases with increase in molar ratio and with a decrease in temperature simultaneously. At higher temperature and at a lower molar ratio lower yield is obtained. Higher molar ratio to reaction temperature that led to the separation of glycerol is complicated, and the yield of biodiesel decreases because a portion of the glycerol remains in the biodiesel phase. Fig. 12.6 indicates the graph plotted to show the effect of molar ratio and catalyst on the yield. From the graph, it is noted that the yield increases as the value of both molar ratio and catalyst increases. For the lower value of catalyst maximum yield occurs at the higher molar ratio and similarly for the lower value of the molar ratio, maximum yield occurs at intermediate catalyst concentration. From the graph, it analyses that maximum yield occurs at the average molar ratio and catalyst concentration. Fig. 12.7 shows the interaction between molar ratio and time to show their effect on yield. From this, at the lower molar ratio and at high reaction time, the transesterification process results in lesser yield and at an intermediate time, and average molar ratio yield is increased. From the graph, it is observed that at low reaction time and yet higher molar ratio maximum yield is obtained. This was mainly due to the transesterification process completed satisfactorily at a lower temperature with enough time in the presence of an alkaline catalyst (sodium methoxide). Fig. 12.8 shows the interaction between molar ratio and speed to show their effect on yield. From this it is
96.00
Predicted yield (%)
73.25
50.50
27.75
5.00 5.00
27.73
50.47 Actual yield (%)
73.20
95.94
FIGURE 12.4 Graphical representation of predicted yield and actual yield.
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12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
Experimental yield
96
81.75
67.5
53.25
39
56.25
12.75 54.38
11.13 52.50
9.50 50.63
B: temperature
7.88
A: molar ratio
48.75 6.25
FIGURE 12.5 Response surface plot of biodiesel yield against molar ratio and temperature.
Experimental yield
80
61.25
42.5
23.75
5
12.75
1.63 1.44
11.13 1.25
C: catalyst
9.50 1.06
7.88
A: molar ratio
0.88 6.25
FIGURE 12.6 Response surface plot of biodiesel yield against molar ratio and catalyst.
concluded that at a constant speed, increase in molar ratio, yield increases up to a certain extent and then it is decreased. It is observed from the graph that at the maximum molar ratio and minimum speed the yield percentage is more. From the observed values, it is noted that maximum yield is obtained at lower values of stirring speed. Further, at the stirring rate above 700 rpm avortex in the liquid phase was createdand lowered its
surface in the central part which resulted in a shorter residence time of methanol bubble in the liquid phase. The residence time of methanol bubble in the liquid phase is important to increase the biodiesel yield. Fig. 12.9 explains the interaction between catalyst concentration and reaction temperature. It is found that at intermediate values of catalyst concentration and lower temperatures, biodiesel yield is maximum.
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12.10 RESULTS AND DISCUSSION
80
Experimental yield
69.5
59
48.5
38
150.00
12.75 135.00
11.13 120.00
9.50 105.00
D: time
7.88
A: molar ratio
90.00 6.25
FIGURE 12.7 Response surface plot of biodiesel yield against molar ratio and time.
Experimental yield
80
69.75
59.5
49.25
39
900.00
12.75 850.00
11.13 800.00
E: speed
9.50 750.00
7.88
A: molar ratio
700.00 6.25
FIGURE 12.8 Response surface plot of biodiesel yield against molar ratio and speed.
From the graph, it is observed that as the temperature increases at constant catalyst concentration, the percentage of biodiesel yield is decreased. This result is due to the negative interaction of reaction temperature and catalyst concentration causes soap formation, which
decreases the yield of biodiesel. The effect of catalyst concentration is more significant than the effect of reaction temperature, but the interaction effect of both the factors is same on the yield. From the figure it is clear that as the temperature increased the amount of yield
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Experimental yield
96 73.25 50.5
27.75 5
56.25
1.63 1.44
54.38 52.50
1.25 1.06
C: catalyst
50.63
B: temperature
0.88 48.75
FIGURE 12.9 Response surface plot of biodiesel yield against temperature and catalyst.
decreased and this is because of triglyceride saponification and the subsequent dissolution of methyl esters into glycerol. Fig. 12.10 indicates that the higher amount of yield occurred with low reaction temperature and at higher reaction time. At higher reaction time and at higher reaction temperature the amount of yield is very less. This is because at higher reaction time and higher reaction temperature the saponification of glycerides gets accelerated by the alkaline catalyst before the completion of transesterification process and also the excessive loss of methanol also leads to decrease in the yield.
Fig. 12.11 points out the interaction between reaction temperature and stirring speed. It indicates that at higher speed and lower temperature the yield obtained is maximum. From the graph, it is clear that at a constant speed as the temperature increases the yield decreases. The main impact of the combination of reaction temperature and stirring speed is that it causes a proper contact between the reagents and the oil during transesterification process. The main reason for the decrease in the amount of yield when temperature and speed increased is because of accelerated saponification reaction. Generally, the impact of stirring speed on the reaction is less and can be neglected.
Experimental yield
96 78.75 61.5 44.25 27
56.25
150.00 54.38
135.00 120.00 D: time
52.50 50.63
105.00
B: temperature
90.00 48.75
FIGURE 12.10
Response surface plot of biodiesel yield against temperature and time. III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
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12.10 RESULTS AND DISCUSSION
96
Experimental yield
81.75
67.5
53.25
39
900.00
56.25 850.00
54.38 52.50
800.00 750.00
E: speed
50.63
B: temperature
700.00 48.75
FIGURE 12.11 Response surface plot of biodiesel yield against temperature and speed.
61
Experimental yield
47 33 19 5
1.63
150.00 135.00
1.44 120.00
D: time
1.25 105.00
1.06 90.00 0.88
C: catalyst
FIGURE 12.12 Response surface plot of biodiesel yield against catalyst and time.
Fig. 12.12 indicates the interaction between catalyst concentration and reaction time. From the graph it is observed that as the catalyst concentration increased at constant time, the biodiesel yield is increased. At higher catalyst concentration and at lower reaction time, higher biodiesel yield is obtained. From the behavior, it is seen that the equilibrium of the reaction reached rapidly at some point and beyond that point the reaction gets stagnated or starts to reverse. Fig. 12.13 explains the interaction between catalyst and speed. From the graph, it is observed that higher stirring speed and higher catalyst concentration produced the highest yield. As the speed
increases at constant catalyst concentration, there is a significant decrease in biodiesel yield. Fig. 12.14 explains the interaction between reaction time and stirring speed. At higher reaction time and higher stirring speed, the yield of biodiesel decreases. This is due to the conversion of triglyceride to an ester by enhanced reaction time. From these response plots, it was observed that the interaction effects of stirring speed were less significant effect on the yield of biodiesel compared to other parameters in the transesterification process. The same was shown in the ANOVA table where speed was not
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73
Experimental yield
56
39
22
5
900.00
1.63 850.00
1.44 1.25
800.00 750.00
E: speed
1.06
C: catalyst
700.00 0.88
FIGURE 12.13
Response surface plot of biodiesel yield against catalyst and speed.
73
Experimental yield
64.5
56
47.5
39
900.00
150.00 850.00
135.00 120.00
800.00 E: speed
750.00
105.00
D: time
700.00 90.00
FIGURE 12.14
Response surface plot of biodiesel yield against time and speed.
significant, and all other parameters were significant. Similar research was observed from other research findings.
12.10.3 Biodiesel analysis After a transesterification reaction, the analytical technique such as Nuclear Magnetic Resonance (NMR) was used to examine the biodiesel verification to inspect the quality of the biodiesel which was suitable for engine
study. Figs. 12.15 and 12.16 shows NMR plot for raw oil and biodiesel, respectively. Interpretation of NMR was conducted using the database of Center for Advanced Research in Indian System of Medicine (CARISM), SASTRA University. The spectra of known compounds stockpiled in Center for Advanced Research in Indian System of Medicine (CARISM) library was differentiated with the spectra of unknown compounds. By comparing the NMR plots of both raw oil and biodiesel, we can observe that at
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315
7.264 5.381 5.371 5.362 5.355 5.352 5.344 5.336 5.325 4.322 4.308 4.283 4.269 4.173 4.154 4.134 2.807 2.789 2.771 2.342 2.336 2.317 2.312 2.292 2.286 2.079 2.059 2.038 2.018 2.001 1.605 1.302 1.254 1.001 0.976 0.951 0.902 0.890 0.880 0.867 0.857 0.000
12.10 RESULTS AND DISCUSSION
5
4
3
2
1
ppm
4.15 9.90 10.71 0.49 3.01
6
2.16 2.98
7
1.00
8
0.70 0.73
9
2.30 0.60
10
FIGURE 12.15 NMR plot for raw oil.
3.6 ppm there was a peak in biodiesel which represents the presence of methyl ester and that peak is not present in the raw oil. The peaks obtained at 3.6 ppm in biodiesel NMR plot have shown the confirmation of methyl ester in the obtained biodiesel.
unsaturated and saturated acids obtained from the GC/MS analysis. Saturated fatty acids and methyl esters improve the stability, increase the cloud point and cetane number.
12.10.4 Gas chromatography/mass spectrometer
12.10.5 Physical and chemical properties of biodiesel
The quality of biodiesel is important for engine study and the analytical method like Gas chromatography/Mass spectrometer (GC/MS) were employed to analyze the products of the transesterification reaction. Fig. 12.17 and Table 12.6 show the GC/MS chromatography of biodiesel. For studying the composition of the biodiesel, gas chromatograph or mass spectroscopy was used (PerkinElmer Clarus 500). The column of the capillary (Column id: 250 mm, Column length: 30 m, Capillary Column type: Elite5MS (5% phenyl 95% dimethylpolysiloxane)) was used for examination FAME. The oventemperature of GC was increased to a final temperature of 280 C from an initial temperature of 60 C. The temperature of injection was kept at 280 C; The carrier gas, helium, was used at a flow rate of 1 mL/min. The analysis of mass detector was analyzed by the specified conditions: electron energy of 70 eV, the carriergas (helium). The biodiesel produced from the inedible oil had the
The Physical and chemical properties of produced biodiesel and raw oil were measured. The results of all the tests are provided in Table 12.7.
12.10.6 Experimental procedure for engine study The test engine used was a four-stroke, naturally aspirated, water-cooled, single-cylinder and direct injection compression injection engine. Its compression ratio is 16.7:1. It has a rated power of 3.7 kW at a constant speed of 1500 rpm. The injection timing and injection pressure set by the manufacturer are 23 degrees before TDC and 200 bar, respectively. Fig. 12.18 shows the schematic view of the engine setup used for this study. The test engine used is directly coupled with an eddy current dynamometer to load the engine. A suitable coupling is provided between the engine and generator to achieve the power transmission without any speed reduction.
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12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
7.280 5.395 5.392 5.380 5.373 5.369 5.361 5.355 5.350 5.343 5.332 5.325 5.306 3.666 3.479 2.827 2.807 2.789 2.771 2.752 2.329 2.304 2.279 2.080 2.060 2.038 2.018 2.000 1.979 1.642 1.619 1.595 1.572 1.304 1.255 1.001 0.976 0.951 0.912 0.901 0.890 0.880 0.867 0.857 –0.00
316
FIGURE 12.16
3
2
1
ppm
2.26 3.26 0.84 2.46 10.58 10.67 0.61 3.00
4
5
1.26
6
7
3.40 2.03
8
9
2.86
10
NMR plot for biodiesel. 15 11×1129 oil sample 26 11 19 29.60 55 29.56 41
100
Scan EI+ TIC 2.80e10
26.56 74
%
0
Time 5.02
FIGURE 12.17
10.02
15.02
20.02
25.02
30.02
35.02
GC/MS chromatography of biodiesel.
The load acting on the engine is varied by changing the current passing through the eddy current dynamometer. A strain gauge which is attached to a torque arm on the dynamometer is used for measuring the force acting on the dynamometer casing from which the torque acting on the dynamometer can be obtained. From this torque, the load acting on the dynamometer, which is same as the load developed by the engine is measured. The load is obtained as the product of torque and angular velocity.
KISTLER quartz transducer was employed to compute the cylinder-pressure. Transducer model 6613 C, with the range of 0e100 bar. The sensor was equipped to measure the in-cylinder pressure in diesel engines. The piezoelectric transducer is selected for accuracy, small size, and its quick response. The transducer should have very high natural frequencies to avoid resonance. The transducer produced a charge output which was relational to the cylinder pressure. The pressure transducer produced electric charge which
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12.10 RESULTS AND DISCUSSION
TABLE 12.6
List of compounds obtained from spectrometry for biodiesel.
S. No.
Peak name
Formula
Molecular weight
Retention time (min)
Peak area
%Peak area
1.
2-Decenal, (Z)
C10H18O
154
12.26
2,557,403
0.7132
2.
2,4-Decadienal, (E,E)-
C10H16O
152
13.06
1,211,714
0.3379
3.
2,4-Decadienal
C10H16O
152
13.61
1,747,760
0.4874
4.
4-Tetradecene, (E)-
C14H28
196
21.77
158,817
0.0443
5.
2-Decene, 9-methyl-, (Z)-
C11H22
154
22.77
130,387
0.0364
6.
Hexadecanoic acid, methyl ester
C17H34O2
270
26.23
1,151,923
0.3212
7.
Palmitic acid
C16H32O2
256
27.46
89,423,504
24.9376
8.
Linoleic acid
C18H32O2
280
30.17
256,056,448
71.4068
9.
Oleic acid
C18H34O2
282
31.59
1,530,239
0.4267
10.
9,17-Octadecadienal, (Z)-
C18H32O
264
33.33
1,407,404
0.3925
11.
Z,Z-3,13-Octadecadien-1-ol
C18H34O
266
33.92
3,212,936
0.8960
TABLE 12.7 S.No.
Properties of diesel, raw oil, and biodiesel. Properties 3
Diesel
Raw oil
Biodiesel
ASTM D6751
1.
Density (kg/m )
824
865
854
D1298
2.
Acid value (mg KOH/g oil)
0
5.34
0.84
D664
3.
0
9
9
D2500
Pour point
( C)
14
5
21
D97
Flash point
( C)
54
321
224
D93
62
334
231
D93
Cloud point
4. 5.
( C)
( C)
6.
Fire point
7.
Kinematic viscosity (cSt)
2.39
25.46
5.11
D445
8.
Calorific value (MJ/Kg)
42
39.66
40.11
D240
9.
Copper strip corrosion
Class 1a
Class 1a
Class 1a
D130
10.
Carbon residue (wt%)
0.0109
0.45
0.2
D189
Fuel flow sensor
Diesel
Bio -diesel
EGR
AVL five gas analyser
Smoke meter
Air flow measurement
Strain guage Calorimeter Surge tank
Orifice plate
Computer UPS
DICI engine
EGR temperature indicator
Crank angle encoder
Coupling
Eddy current dynamometer
FIGURE 12.18 Schematic diagram of the engine experimental setup.
318
12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
was converted to the analog voltage reading with the help of charge amplifier. This charge output was then fed to combustion analyzer to evaluate and determine cylinder combustion characteristics and peak pressure balance. For crank angle measurement KueblerSendix 5000 TDC marker was used. This type of encoder is used wherever engine angle and flow information are needed to calculate the combustion parameters and heat release rate of an engine. The experimental procedure implemented to conduct the test on a diesel engine is discussed in this section. The crank lever was used to start the test engine. The engine was permitted to reach steady-state. The engine cooling was achieved by circulating water through the cylinder head and the jackets of the engine block. SAE 20W-40 oil was used as lubricating oil in a diesel engine. Some trial tests were made to verify, correct, and calibrate all the measuring instruments. The readings were taken thrice to secure repeatability of the data and mean of all three readings were considered in the present investigation. The following biodiesel blends, for example, B100, B40, B20, and B10 were considered based on the literature surveyed for engine study and compared with biodiesel and diesel with standard operating conditions. In order to provide a database to compare test fuels, a thorough investigation on the engine was completed using diesel as the baseline at standard operating conditions (200 bar and 23 bTDC). AVL digas 444 five gas analyzer was used to measure the concentration of CO, CO2, NO, O2, and HC present in the exhaust gas. The concentration of HC and NO are measured in ppm volume, whereas those of CO, CO2, and O2 are expressed regarding percentage volume. For determining the concentration of gaseous pollutants in the exhaust, a sample was taken from a region near to the exhaust valve.
12.10.6.1 Brake thermal efficiency BTE for biodiesel and its blends increases up to the rated load of the engine and then starts decreasing as shown in Fig. 12.19. The maximum BTE for diesel, B10, B20, B40 and B100 was found to be 24.8%, 22.4%, 22.17%, 21.79%, and 21.37%, respectively for 4.0968 BMEP. The variation of BTE was shown in Fig. 12.20 for biodiesel and its blends. Compared to diesel, the BTE was decreased in biodiesel and its blends. The decrease in brake thermal efficiency can be attributed to the fact the calorific value of biodiesel is 40.11 MJ/ kg while that for diesel is 42 MJ/kg. So, with an increase in blending there is a decrease in the calorific value and hence, decrease in BTE.
12.10.6.2 Brake-specific energy consumption (BSEC) Fig. 12.20 shows the variation of BSEC for biodiesel and its blends were compared with diesel. BSEC is the ratio of energy obtained by burning fuel for an hour to brake power. It is an indicator of how effectively the energy obtained from the fuel is. BSEC ¼ Brake specific fuel consumption calorific value of fuel Fig. 12.20 shows that, with an increase in load, the BSEC decreases. At full load condition, the BSEC value is 12.5 MJ/kWh for diesel, 16.04 MJ/kWh for B10 blend, 16.24 MJ/kWh for B20,16.51 MJ/kWh for B40 blend, and for B100 blend it is 16.99 MJ/kWh. At full-load condition, The BSEC for biodiesel and its blends are showing similar value, and it was higher than diesel. The BSEC for B100 is greater than that of diesel, B10, B20, and B40
30
25
BTE(%)
20
15 B100 B40 B20 B10 Diesel
10
5
0 1
2
3
4
5
6
BMEP (bar)
FIGURE 12.19
Variation of brake thermal efficiency for biodiesel and its blends.
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319
12.10 RESULTS AND DISCUSSION
60
B100 B40 B20 B10 Diesel
50
BSEC
40
30
20
10 0
1
2
3
4
5
6
BMEP(bar)
FIGURE 12.20 Variation of brake-specific energy consumption for biodiesel and its blends.
at partial loading condition. BSEC decreased with an increment of blend ratio of diesel at partial loading condition. 12.10.6.3 Heat release rate Fig. 12.21 shows the variation of heat release rate with BMEP. From the figure, it clearly shows that maximum heat release rate occurs for diesel and then it decreases continuously for biodiesel blends and is least for B100. Even though biodiesel has more oxygen content, it cannot produce more energy than diesel. Heat release rate does not depend on only onefactordoxygen content, it also depends on calorific value, C-H value, and latent heat of vaporization. Biodiesel has less calorific value compared to diesel, so the heat release rate for
diesel is higher than that of biodiesel. It is observed that the heat release rate of diesel is 56.8740 J/deg CA at 2 aTDC and for B100 the heat release rate value is 42.530 J/ CA at 7 aTDC. 12.10.6.4 Ignition delay Fig. 12.22 shows a variation of ignition delay with BMEP. From the figure, it is clear that diesel has more delay period compared to biodiesel. Generally, biodiesel has a high cetane number; ignition quality is more because of high cetane number which reduces the delay period. Since diesel has less cetane number ignition delay period will be more as compared to biodiesel. It is observed that at full-load operating condition ignition delay periods for diesel, B10, B20, B40, and
60 B100 B40 B20 B10 Diesel
Heat release rate(J/deg CA)
50 40 30 20 10 0 –10 –40
–20
0t
20
40
Crank Angle(degree)
FIGURE 12.21 Variation of heat release rate for biodiesel and its blends.
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12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
Diesel B10 B20 B40 B100
Ignition duration (degree CA)
20
15
10
5
0 0
1
2
3
4
5
6
BMEP (bar)
FIGURE 12.22
Variation of ignition delay for biodiesel and its blends.
B100 are 13.98 CA, 13.56 CA, 13.31 CA, 13.16 CA, and 13.01 CA, respectively. 12.10.6.5 Cylinder gas peak pressure The peak pressure occurred inside the cylinder during the combustion is termed as cylinder gas peak pressure. Fig. 12.23 shows the comparison of cylinder gas peak pressure for diesel and blends of biodiesel at different loads. From the figure, it is clear that diesel has high peak pressure value compared to biodiesel. The reason behind this statement is diesel has more ignition delay which results in more accumulation of fuel inside the cylinder increase the uncontrolled combustion phase, thus causing high pressure inside the cylinder. It is observed that at full-load condition the peak pressure
values for diesel is 64.85 bar, B10 is 64.13 bar, B20 is 63.757 bar, B40 is 62.116 bar, and for B100 is 60.08 bar, respectively. 12.10.6.6 Combustion duration Fig. 12.24 shows the variation of combustion duration with BMEP. Combustion duration is the one which gives the value of how much duration it took for the complete combustion of fuel. From the figure, it is clear that for all the loads, diesel is having less combustion duration whereas B100 has more combustion duration and also it is clear that as the load increases combustion duration also increases for all the fuel blends. Due to more ignition delay period in diesel, more fuel gets accumulated into the cylinder, and the total fuel is ready for
Cylinder gas peak pressure (bar)
100 B100 B40 B20 B10 Diesel
80
60
40
20
0 0
FIGURE 12.23
1
2
3 BMEP (bar)
4
5
6
Variation of cylinder gas peak pressure for biodiesel and its blends.
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12.10 RESULTS AND DISCUSSION
Combustion duration (degree CA)
140 Diesel B10 B20 B40 B100
120 100 80 60 40 20 0 0
1
2
3 4 BMEP (bar)
5
6
FIGURE 12.24 Variation of combustion duration for biodiesel and its blends.
atomization, and also proper mixing takes place, so the combustion duration is less compared to other biodiesel blends, and also as latent heat of vaporization is more for biodiesel compared to diesel, biodiesel takes more time to get vaporized which leads to longer combustion duration compared to diesel. 12.10.6.7 Exhaust gas temperature Fig. 12.25 shows the variation of exhaust gas temperature with BMEP. As the delayed combustion for B100 the exhaust gas temperature higher compared to diesel and other blends. The in-cylinder temperature is comparatively higher for B100 due to higher viscosity and poor atomization causes for delayed combustion, so the temperature carried away by the exhaust gases is more compared to diesel. It is observed at full load operating condition, the exhaust temperatures for diesel,
12.10.6.8 Carbon monoxide Fig. 12.26 shows the variation of carbon monoxide emission with BMEP. Presence of CO indicates incomplete combustion and lack of oxygen for combustion. The initial CO emissions are almost the same for diesel, B10, B20, B40, as well as B100 blends. At full load, the CO emission shows 1.10 vol% for diesel, 1.00 vol% for B10 blend, 0.8 vol% for B20 and 0.76 vol% for B40, 0.72 vol % for B100. The CO emission for B100 is lower than that of B40, B20, and B10 which are lesser than that of diesel. The reason for the decrease in the CO volume can be attributed to the presence of oxygen in biodiesel while diesel has no oxygen content at all. So, as the blending percentage increases, there is comparatively
Diesel B10 B20 B40 B100
200 Exhaust gas temperature (°C)
B10, B20, B40, and B100 are 131.89, 133.91 149.35, 155.45 and 156.09 C, respectively.
150
100
50
0 0
1
2
3 BMEP (bar)
4
5
6
FIGURE 12.25 Variation of exhaust gas temperature for biodiesel and its blends.
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12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
1000
1.2 1.0
B100 B40 B20 B10 Diesel
NO(ppm)
CO (%)
0.8
B100 B40 B20 B10 Diesel
800
0.6
600
400
0.4 200
0.2 0.0 0
1
2
3 BMEP (bar)
4
5
0
6
FIGURE 12.26 Variation of carbon monoxide for biodiesel and its
0
FIGURE 12.28
1
2
3 BMEP(bar)
4
5
6
Variation of nitric oxide for biodiesel and its blends.
blends.
more oxygen available in the engine and combustion becomes more efficient. 12.10.6.9 Carbon dioxide Fig. 12.27 shows the variation of CO2 with BMEP. The CO2 content increases with an increase in load, since with increasing load more fuel will be burnt. The fuel will shift from diesel to B10, B20, B40, and B100 blend; the CO2 volume percentage increases under all operating conditions. At full-load condition, 7.5670 vol% of CO2 is formed in diesel combustion, 10.5 vol%, 10.9 vol %, 10.5 vol%, and 11.1 vol% of CO2 is formed in B10, B20, B40, and B100, respectively. This is because oxygen content is more in biodiesel as a result of which an increase in the biodiesel ratio increased the CO2 formation. 12.10.6.10 Nitric oxide Nitric oxide emission is harmful emission which is produced during the uncontrolled combustion phase.
The NO formation depends upon the availability of oxygen content and the in-cylinder temperature. Fig. 12.28 shows the variation of nitric oxide (NO) emissions with BMEP. As the load increases, NO emissions increase for all the fuels. At full load, NO emissions reached 835 ppm for diesel, 850 ppm for B10, 856 ppm for B20, 864 ppm for B40, and 883 ppm for B100. Thus, NO emission was higher for B100 compared to B40, B20, B10, and diesel. No emission was increased with increase in biodiesel concentration. The premixed combustion is more efficient with an increase in the blending due to a higher amount of oxygen present in the biodiesel. The in-cylinder temperature is comparatively higher due to higher heating and thus NO emissions increase. 12.10.6.11 Unburned hydrocarbons Fig. 12.29 shows the variation of Unburned Hydrocarbon emissions (UBHC) with BMEP. A UBHC emission results from the part of the fuel that does not take part 140
12
B100 B40 B20 B10 Diesel
8
Unburned HC(ppm)
CO2 (%)
10
6 4 2
100 80 60 40 20
0 0
FIGURE 12.27 blends.
B100 B40 B20 B10 Diesel
120
1
2
3 BMEP (bar)
4
5
6
Variation of carbon dioxide for biodiesel and its
0
0
FIGURE 12.29
1
2
3 BMEP(bar)
4
5
6
Variation of unburned hydrocarbons for biodiesel
and its blends.
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323
NOMENCLATURE
in the combustion, that is, complete combustion does not take place. At full load, 122 ppm of UBHC is produced by diesel, 112 ppm by B10, 92 ppm by B20, 89 ppm by B40, and 81 ppm by B100. The higher oxygen content in biodiesel and its blends is the reason for which their combustion is relatively more efficient when compared with pure diesel. As the blending ratio decreases progressively with B10, B20, B40, and B100, the oxygen percentage increases and thus combustion becomes more and more efficient resulting in lower UBHC emissions. 12.10.6.12 Filter smoke number The filtered soot causes blackening of the filter paper, which is measured by a photoelectric measuring head and the result is analyzed by a microprocessor. The determined value is the Filter Smoke Number (FSN). Fig. 12.30 shows the variation of FSN with BMEP. FSN increases with load. FSN is the index which measures the amount of carbon particle (soot) available in the exhaust. The FSN value for diesel is higher than that of B10, B20, B40, and B100 blends. It is due to thisfact combustion is proper as the blending percentage increases. At the rated load, the FSN value for diesel, B10, B20, B40, and B100 are 8.88, 7.486, 7.29, 7.41, and 6.83, respectively. Higher oxygen content and proper combustion will lead to lower smoke emission for biodiesel and its blends compared to diesel.
12.11 CONCLUSIONS The study concentrates on biodiesel production and also concentrates on identifying the optimum conditions. From the study, biodiesel production is optimized through response surface methodology (RSM). The 10
Filter smoke number
8
B100 B40 B20 B10 Diesel
6
4
2
0 0
1
2
3
4
5
6
BMEP(bar)
FIGURE 12.30 and its blends.
Variation of unburned hydrocarbons for biodiesel
performance, combustion, and emission analysis of obtained biodiesel and its blends were carried out by using a single-cylinder four-stroke diesel engine. The following conclusions are drawn from this work, and it is listed below. • The optimal condition for production of methyl ester was the following: temperature 45 C, time 120 min, molar ratio 9:1 (methanol:oil), catalyst concentration 1.25 wt%, and 800 rpm stirrer speed. At this optimized condition, the yield of purified biodiesel was 95.4%. • The acid value of the final biodiesel was estimated as 0.84 mg of KOH/g of oil. Based on that it was concluded that single stage transesterification was enough to produce fatty acid methyl ester (FAME). • It was observed that the brake thermal efficiency of the biodiesel (B100) is 3.5% less as compared to that of diesel. • At rated load, the brake specific energy consumption for B100 is 36% higher than diesel. The brake specific energy consumption decreased with increase in biodiesel blend. • NO emission for biodiesel (B100) was 6% higher than diesel at full-load condition. Similarly, unburnt hydrocarbon and smoke emission were lower than diesel by 22% and 23%, respectively. • It is observed that at full-load conditions, CO2 emissions for biodiesel are 4% higher than diesel and CO emission 0.4% lower than diesel due to higher oxygen concentration resulting in complete combustion of biodiesel.
NOMENCLATURE ANOVA ASTM B100 B20 B50 BSEC BSFC BTE CCD CH3ONa CI CO CO2 DJO DJO10 DLF DoE EGR EGT EN FAAE FAEE
analysis of variance American Society for Testing Material 100% biodiesel 20% biodiesel þ 80% diesel 50% biodiesel þ 50% diesel brake-specific energy consumption brake-specific fuel consumption brake thermal efficiency (%) central composite design sodium methoxide combustion ignition carbon monoxide carbon dioxide Degummed jatropha oil 10% degummed jatropha oil þ 90% diesel diesel-likefuel design of experiment exhaust gas recirculation exhaust gas temperature European norms fatty acyl acid ester fatty acid ethyl ester
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324 FAME FSN GCMS GHG H2SO4 HC JCO JO JO10 KOH LHR LOME NaOH NCV NMR NO NOx OPEC PM REE RME RSM SOx SVO TAG TBC TDC UBHC
12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
fatty acid methyl ester filter smoke number gas chromatography massspectroscopy green house gas sulfuric acid hydrocarbon Jatropha curcas oil jatropha oil 10% jatropha oil þ 90% diesel potassium hydroxide low heat rejection linseed oil methyl ester sodium hydroxide net calorific value nuclear magnetic resonance nitric oxide nitrogen oxides Organization of the Petroleum Exporting Countries particulate matter rapeseed ethyl ester rapeseed methyl ester response surface methodology sulfur dioxides straight vegetable oil triglycerides thermal barrier coating top dead center unburned hydrocarbon (ppm)
Acknowledgments This work was supported by the Department of Science and Technology, New Delhi, India, and the Director, National Institute of Technology, Tiruchirappalli, India for extending the facilities to carry out the research work.
References [1] Khosravi E, Shariati A, Nikou MRK. Instant biodiesel production from waste cooking oil under industrial ultrasonic irradiation. Int J Oil Gas Coal Technol 2016;11(3). [2] Prabhakar S, Banugopan VN, Annamalai K, Jayaraj S. Analysis of chosen parameters of CI engine for nerium oil - an alternative fuel. In: Proceedings of the international conference on frontiers in automobile and mechanical engineering - 2010, FAME-2010; 2010. p. 88e91. [3] The International Energy Agency (IEA). World energy outlook 2006. OECD/IEA; 2006. [4] Kankia AI, Musa A, Daha A, Ishaq U. Production, characterization and process variables of biodiesel from non-edible plant oil (neem &soapnut): a review. Int J Sci Res 2014;3(11). [5] REN21 Renewables 2010 Global Status Report. Renewables 2010 global status report. Paris: REN21 Secretariat; 2010. p. 15. [6] Chhetri AB, Tango MS, Budge SM, Watts KC, Islam MR. Nonedible plant oils as new sources for biodiesel production. Int J Mol Sci 2008;9(2):169e80. [7] Manickam S, Arigela VND, Gogate PR. Intensification of synthesis of biodiesel from palm oil using multiple frequency ultrasonic flow cell. Fuel Process Technol 2014;128:388e93. [8] Lay L, MyintMahmoud M, El-Halwagi. Process analysis and optimization of biodiesel production from soybean oil. Clean Technol Environ Policy 2009;11(3):263e76.
[9] Atabani AE, Ce´sar ADS. Calophyllum inophyllum L. e a prospective non-edible biodiesel feedstock. Study of biodiesel production, properties, fatty acid composition, blending and engine performance. Renew Sustain Energy Rev 2014;37:644e55. [10] Ahmad AL, Yasin NHM, Derek CJC, Lim JK. Microalgae as a sustainable energy source for biodiesel production: a review. Renew Sustain Energy Rev 2011;15(1):584e93. [11] Demirbas A, Bafail A, Ahmad W, Sheikh M. Biodiesel production from non-edible plant oils. Energy Explor Exploit 2016;34:290e318. [12] Devan PK, Mahalakshmi NV. Study of the performance, emission and combustion characteristics of a diesel engine using poon oil-based fuels. Fuel Process Technol 2009;90(4):513e9. [13] Srivastava A, Prasad R. Triglycerides-based diesel fuels. Renew Sustain Energy Rev 2000;4(2):111e33. [14] Ramachandran S, Singh SK, Larroche C, Soccol CR, Pandey A. Oil cakes and their biotechnological applications - a review. Bioresour Technol 2007;98(10):2000e9. [15] Nye MJ, Southwell PH. Esters from rapeseed oil as diesel fuel. In: Proc. Vegetable oil as diesel fuel Seminar III Peoria. IL: Northern Agricultural Energy Centre; 1983. p. 77e83. [16] Cvengros J, Povazanec F. Production and treatment of rapeseed oil methyl esters as alternative fuels for diesel engines. Bioresour Technol 1996;55(2):145e50. [17] Labeckas G, Slavinskas S. The effect of rapeseed oil methyl ester on direct injection Diesel engine performance and exhaust emissions. Energy Convers Manag 2006;47(13e14):1954e67. [18] Rashid U, Anwar F, Moser BR, Knothe G. Moringa oleifera oil: a possible source of biodiesel. Bioresour Technol 2008;99(17): 8175e9. [19] Kafuku G, Mbarawa M. Alkaline catalyzed biodiesel production from moringa oleifera oil with optimized production parameters. Appl Energy 2010;87(8):2561e5. [20] Saydut A, Duz MZ, Kaya C, Kafadar AB, Hamamci C. Transesterified sesame (Sesamum indicum L.) seed oil as a biodiesel fuel. Bioresour Technol 2008;99(14):6656e60. [21] C ¸ aynak S, Gu¨ru¨ M, Bic¸er A, Keskin A, Ic¸ingu¨r Y. Biodiesel production from pomace oil and improvement of its properties with synthetic manganese additive. Fuel 2009;88(3):534e8. [22] De BK, Bhattacharyya DK. Biodiesel from minor vegetable oils like karanja oil and nahor oil. Lipid e Fett 1999;101(10):404e6. [23] Sharma YC, Singh B, Korstad J. Application of an efficient nonconventional heterogeneous catalyst for biodiesel synthesis from pongamia pinnata oil. Energy Fuels 2010;24(5):3223e31. [24] Jain S, Sharma MP. Kinetics of acid base catalyzed transesterification of Jatropha curcas oil. Bioresour Technol 2010;101(20):7701e6. [25] Sahoo PK, Das LM, Babu MKG, Arora P, Singh VP, Kumar NR, et al. Comparative evaluation of performance and emission characteristics of jatropha, karanja and polanga based biodiesel as fuel in a tractor engine. Fuel 2009;88(9):1698e707. [26] Puhan S, Jegan R, Balasubbramanian K, Nagarajan G. Effect of injection pressure on performance, emission and combustion characteristics of high linolenic linseed oil methyl ester in a DI diesel engine. Renew Energy 2009;34(5):1227e33. [27] Ma F, Hanna MA. Biodiesel production: a review. Bioresour Technol 1999;70:1e15. [28] Demirbas A. Biodiesel from vegetable oils via transesterification in supercritical methanol. Energy Convers Manag 2002;43: 2349e56. [29] Vaıtilingom G. Huiles ve´ge´talesdbiocombustible diesel. Influence de la nature des huiles et en particulier de leur composition en acides gras sur la qualite´ -carburant. Universite´ d’Orleans; 1992. [30] Agarwal D, Agarwal AK. Performance and emissions characteristics of jatropha oil (preheated and blends) in a direct injection compression ignition engine. Appl Therm Eng 2007;27: 1314e2323.
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
REFERENCES
[31] Cert A, Moreda W, Perez-Camino MC. Chromatographic analysis of minor constituents in vegetable oils. J Chromatogr A 2000;881:131e48. [32] Gonfa Keneni Y, Mario Marchetti J. Oil extraction from plant seeds for biodiesel production. AIMS Energy 2017;5(2):316e40. Available from: http://www.aimspress.com/article/10.3934/ energy.2017.2.316. [33] Mahanta P, Shrivastava A. Technology development of bio-diesel as an energy alternative. In: Challenges Strategy Sustain Energy Deficiency and Environment; 2012. p. 1e19. Available from: http://www.newagepublishers.com/samplechapter/001305. pdf. [34] Achten WMJ, Verchot L, Franken YJ, Mathijs E, Singh VP, Aerts R, et al. Jatropha bio-diesel production and use. Biomass Bioenergy 2008;32(12):1063e84. [35] Bhargavi G, Nageswara Rao P, Renganathan S. Review on the extraction methods of crude oil from all generation biofuels in last few decades. IOP Conf Ser Mater Sci Eng 2018;330(1). [36] Weiss EA. Oilseed crops. Longman Group Ltd; 1983. p. 31e99. [37] Muzenda E, Kabuba J, Mdletye P, Belaid M. Optimization of process parameters for castor oil production. Proc World Congr Eng 2012;3:5401e14. [38] Atabani AE, Silitonga AS, Ong HC, Mahlia TMI, Masjuki HH, Badruddin IA, et al. Non-edible vegetable oils: a critical evaluation of oil extraction, fatty acid compositions, biodiesel production, characteristics, engine performance and emissions production. Renew Sustain Energy Rev 2013;18:211e45. Available from: http://linkinghub.elsevier.com/retrieve/pii/ S1364032112005552. [39] Verdugo C, Luna D, Posadillo A, Sancho ED, Rodrı´guez S, Bautista F, et al. Production of a new second generation biodiesel with a low cost lipase derived from Thermomyces lanuginosus: optimization by response surface methodology. Catal Today 2011:107e12. [40] Meher LC, Vidya Sagar D, Naik SN. Technical aspects of biodiesel production by transesterificationda review. Renew Sustain Energy Rev 2006;10:248e68. [41] Balat M, Balat H. Progress in biodiesel processing. Appl Energy 2010;87:1815e35. [42] Gurunathan B, Ravi A. Process optimization and kinetics of biodiesel production from neem oil using copper doped zinc oxide heterogeneous nanocatalyst. Bioresour Technol 2015;190:424e8. [43] Latchubugata CS, Kondapaneni RV, Patluri KK, Virendra U, Vedantam S. Kinetics and optimization studies using Response Surface Methodology in biodiesel production using heterogeneous catalyst. Chem Eng Res Des July 1, 2018;135:129e39. Available from: https://www.sciencedirect.com/science/article/pii/ S0263876218302612. [44] Muthukumaran C, Praniesh R, Navamani P, Swathi R, Sharmila G, Manoj Kumar N. Process optimization and kinetic modeling of biodiesel production using non-edible Madhuca indica oil. Fuel 2017;195:217e25. [45] Ma Y, Wang Q, Sun X, Wu C, Gao Z. Kinetics studies of biodiesel production from waste cooking oil using FeCl3-modified resin as heterogeneous catalyst. Renew Energy 2017;107:522e30. [46] Ullah Z, Bustam MA, Man Z, Khan AS, Muhammad N, Sarwono A. Preparation and kinetics study of biodiesel production from waste cooking oil using new functionalized ionic liquids as catalysts. Renew Energy 2017;114:755e65. [47] Sidibe´ SS, Blin J, Vaitilingom G, Azoumah Y. Use of crude filtered vegetable oil as a fuel in diesel engines state of the art: literature review. Renew Sustain Energy Rev 2010;14(9): 2748e59. [48] Higelin P. Huiles ve´ge´talesdbiocombustible diesel. Incidence des aspects thermiques lie’ s au type de moteur sur la combustion. Orle´ans: Universite´ d’Orle´ans; 1992.
325
[49] Sirisomboon P, Kitchaiya P, Pholpho T, Mahuttanyavanitch W. Physical and mechanical properties of Jatropha curcas L. fruits, nuts and kernels. Biosyst Eng 2007;97:201e7. [50] Openshaw K. A review of Jatropha curcas: an oil plant of unfulfilled promise. Biomass Bioenergy 2000;19:1e15. [51] Sidibe´ SS, Blin J, Vaitilingom G, Azoumah Y. Use of crude filtered vegetable oil as a fuel in diesel engines state of the art: literature review. Renew Sustain Energy Rev 2010;14:2748e59. [52] Van Grepen J. Cetane number testing of biodiesel. In: Proceedings from the 3rd liquid fuels and industrial products from renewable resources conference; 1996. [53] Ramadhas AS, Jayaraj S, Muraleedharan C. Use of vegetable oils as I.C. engine fuelsda review. Renew Energy 2004;29:727e42. [54] Murugesan A, Umarani C, Subramanian R, Nedunchezhian N. Bio-diesel as an alternative fuel for diesel enginesda review. Renew Sustain Energy Rev 2008. [55] Labeckas G, Slavinskas S. Performance of direct-injection offroad diesel engine on rapeseed oil. Renew Energy 2006;31: 849e63. [56] Zhu RJ, Wang XB, Miao H, Huang ZH. Combustion and particulate emission characteristics of a diesel engine fuelled with diesel-dimethoxymethane blends. Proc Inst Mech Eng - Part D J Automob Eng 2010;224(4):521e31. [57] Adaileh WM, Alqdah KS. Performance of diesel engine fuelled by a biodiesel extracted from a waste cocking oil. In: Energy procedia; 2012. p. 1317e34. [58] Devan PK, Mahalakshmi NV. Combustion, emission and performance characteristics of diesel engine fueled with Eucalyptus oil with an ignition enhancer. Int J Green Energy 2010;1(1):40e9. [59] Hassan MH, Kalam MA. An overview of biofuel as a renewable energy source: development and challenges. In: Procedia engineering; 2013. p. 39e53. [60] Ghorbani A, et al. A comparative study of combustion performance and emission of biodiesel blends and diesel in an experimental boiler. Appl Energy 2011;88:4725e32. [61] Huang D, Zhou H, Lin L. Biodiesel: an alternative to conventional fuel. In: Energy procedia; 2011. p. 1874e85. [62] Mostafa SSM, El-Gendy NS. Evaluation of fuel properties for microalgae Spirulina platensis bio-diesel and its blends with Egyptian petro-diesel. Arab J Chem 2017;10:S2040e50. [63] Pradhan P, Chakraborty S, Chakraborty R. Optimization of infrared radiated fast and energy-efficient biodiesel production from waste mustard oil catalyzed by Amberlyst 15: engine performance and emission quality assessments. Fuel 2016;173:60e8. [64] Prabhahara M, Rajanb K, Krishnamoorthi S. Performance and emission characteristics of diesel engine with mustard oildiesel blends as fuel. Int J Chem Sci 2016;14(S2):655e64. [65] Kalam MA, Husnawan M, Masjuki HH. Exhaust emission and combustion evaluation of coconut oil-powered indirect injection diesel engine. Renew Energy 2003;28(15):2405e15. [66] Tippayawong N, Permsuwan A, Vorayos N, Kiatsiriroat T, Uppakam S, Panyacum M. Long term direct injection diesel engine operation on vegetable oil/diesel blends. SAE Tech Pap 2003. [67] Bari S, Yu CW, Lim TH. Performance deterioration and durability issues while running a diesel engine with crude palm oil. Proc Inst Mech Eng Part D 2002;216:785e92. [68] Nettles-Anderson S, Olsen D. Survey of straight vegetable oil composition impact on combustion properties. SAE Tech Pap 2009:1e487. [69] Murugesan A, Umarani C, Subramanian R, Nedunchezhian N. Bio-diesel as an alternative fuel for diesel engines-A review. Renew Sustain Energy Rev 2009;13:653e62. [70] Schlick ML, Hanna MA, Schinstock JL. Soybean and sunflower oil performance in a diesel engine. Trans Am Soc Agric Eng 1988;31(5).
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
326
12. PERFORMANCE, COMBUSTION, AND EMISSION CHARACTERISTICS OF DI DIESEL ENGINE USING MAHUA BIODIESEL
[71] Machacon HTC, Matsumoto Y, Ohkawara C, Shiga S, Karasawa T, Nakamura H. The effect of coconut oil and diesel fuel blends on diesel engine performance and exhaust emissions. JSAE Rev 2001;22(3):349e55. [72] Reksowardojo IK, Lubis IH, Manggala W, Brodjonegoro TP, Soerawidjaja TH, Arismunandar W, et al. Performance and exhaust gas emissions of using biodiesel fuel from physic nut (Jatropha curcas L.) oil on a direct injection diesel engine (DI). SAE Tech Pap 2007:1232e6. [73] Agarwal D, Kumar L, Agarwal AK. Performance evaluation of a vegetable oil fuelled compression ignition engine. Renew Energy 2008;33(6):1147e56. [74] Agarwal AK, Dhar A. Performance, emission and combustion characteristics of jatropha oil blends in a direct injection CI engine. SAE Tech Pap 2009. [75] Singh SP, Singh D. Bio-diesel production through the use of different sources and characterization of oils and their esters as the substitute of diesel: a review. Renew Sustain Energy Rev 2010;14:200e16. [76] Agarwal AK, Dhar A. Experimental investigations of engine durability and lubricating oil properties of jatropha oil blends fuelled Dl diesel engine. In: Proceedings of the ASME internal combustion engine division fall technical conference 2009; 2009. p. 137e47. [77] Anand R, Kannan GR, Nagarajan S, Velmathi S. Performance emission and combustion characteristics of a diesel engine fueled with biodiesel produced from waste cooking oil. SAE Tech Pap 2010. [78] Rakopoulos CD, Hountalas DT, Zannis TC. Theoretical study concerning the effect of oxygenated fuels on di diesel engine performance and emissions. SAE Tech Pap 2004. [79] Lapuerta M, Armas O, Rodrı´guez-Ferna´ndez J. Effect of biodiesel fuels on diesel engine emissions. Prog Energy Combust Sci 2008;34:198e223. [80] Masjuki H, Abdulmuin MZ, Sii HS. Investigations on preheated palm oil methyl esters in the diesel engine. Proc Inst Mech Eng Part A 1996;210(2). [81] Yucesu HS, Ilkilic C. Effect of cotton seed oil methyl ester on the performance and exhaust emission of a diesel engine. Energy Sources Part A 2006;28(4):389e98. [82] Srinivasa Rao P, Gopalakrishnan VK. Vegetable oils and their methyl esters as fuels for diesel engines. Ind J Technol 1991;29: 292e7. [83] Ahmed MA, Ejim CE, Fleck BA, Amirfazli A. Effect of biodiesel fuel properties and its blends on atomization. SAE Tech Pap 2006;2006(724). [84] Tat ME, Van Gerpen JH, Soylu S, Canakci M, Monyem A, Wormley S. Speed of sound and isentropic bulk modulus of biodiesel at 21 C from atmospheric pressure to 35 MPa. J Am Oil Chem Soc 2000;77(3):285e9. [85] Oman H. Energy sources for the world’s post-petroleum era. IEEE Aerosp Electron Syst Mag 2003;18:35e9. [86] Raheman H, Ghadge SV. Performance of diesel engine with biodiesel at varying compression ratio and ignition timing. Fuel 2008;87(12):2659e66. [87] Raheman H, Ghadge SV. Performance of compression ignition engine with mahua (Madhuca indica) biodiesel. Fuel 2007;86(16): 2568e73. [88] Usta N. An experimental study on performance and exhaust emissions of a diesel engine fuelled with tobacco seed oil methyl ester. Energy Convers Manage 2005;46:2373e86. [89] Thornton M. Fuel effects issues for in-use diesel applications. In: Presented at. NAMVECC conference. Chattanooga [TN]; November 4, 2003. p. 104.
[90] McCormick RL, Alvarez JR, Graboski MS. NO x solutions for biodiesel NOx solutions for biodiesel final report. Contract 2003; 1e49. [91] Islam MA, Ayoko GA, Brown R, Stuart D, Heimann K. Influence of fatty acid structure on fuel properties of algae derived biodiesel. In: Procedia engineering; 2013. p. 591e6. [92] Knothe G. Improving biodiesel fuel properties by modifying fatty ester composition. Energy Environ Sci 2009;2(7):759. [93] Puhan S, Vedaraman N, Sankaranarayanan G, Ram BVB. Performance and emission study of Mahua oil (madhuca indica oil) ethyl ester in a 4-stroke natural aspirated direct injection diesel engine. Renew Energy 2005;30(8):1269e78. [94] Sethi VP, Salariya KS. Exhaust analysis and performance of a single cylinder diesel engine run on dual fuels. J Inst Eng Mech Eng Div 2004;85(1 Apr):1e7. [95] Ramadhas AS, Muraleedharan C, Jayaraj S. Performance and emission evaluation of a diesel engine fueled with methyl esters of rubber seed oil. Renew Energy 2005;30(12):1789e800. [96] Agarwal AK, Das LM. Biodiesel development and characterization for use as a fuel in compression ignition engines. J Eng Gas Turbines Power 2001;123(2):440. [97] Tatarnikov AP, Shustrov FA, Lezhnev LY, Petrichenko DA, Papkin IA. Combined supercharging systems and downsizing as the modern trends in the development of vehicle engines. Int J Appl Eng Res 2016;11(22):10975e9. ISSN 09734562. [98] Hu B, Turner JWG, Akehurst S, Brace C, Copeland C. Observations on and potential trends for mechanically supercharging a downsized passenger car engine:a review. Proc Inst Mech Eng - Part D J Automob Eng 2017;231:435e56. [99] Giakoumis EG. Review of some methods for improving transient response in automotive diesel engines through various turbocharging configurations. Front Mech Eng 2016;2. [100] Colban WF, Miles PC, Oh S. Effect of intake pressure on performance and emissions in an automotive diesel engine operating in low temperature combustion regimes. SAE: 2007:01-4063. 2007. [101] Karabektas M. The effects of turbocharger on the performance and exhaust emissions of a diesel engine fuelled with biodiesel. Renew Energy 2009;34(4):989e93. [102] Al-Hinti I, Samhouri M, Al-Ghandoor A, Sakhrieh A. The effect of boost pressure on the performance characteristics of a diesel engine: a neuro-fuzzy approach. Appl Energy 2009;86(1): 113e21. [103] Nayak SK, Pattanaik BP. Experimental investigation on performance and emission characteristics of a diesel engine fuelled with mahua biodiesel using additive. In: Energy procedia; 2014. p. 569e79. [104] Jawre SS, Bhagat A, Moghe SM, Pakhale VA. Diethyl ether as additive and its effect on diesel engine performance e areview. Global Res Dev J Eng 2016;1(5). [105] Arpa O, Yumrutas R, Demirbas A. Production of diesel-like fuel from waste engine oil by pyrolitic distillation. Appl Energy 2010; 87(1):122e7. [106] Guan G, Kusakabe K, Yamasaki S. Tri-potassium phosphate as a solid catalyst for biodiesel production from waste cooking oil. Fuel Process Technol 2009;90(4):520e4. [107] Heywood JB. Internal combustion engine fundamentals. McGrawHill series in mechanical engineering, vol. 21; 2011. 930 p. [108] Tuteja AD, Hoffman MB, Lopez-Crevillen JM, Singh S, Stomber RR, Wallace GC. Selection and development of a particulate trap system for a light duty diesel engine. SAE Technical Paper 920142. 1992.
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS
FURTHER READING
[109] Bhaskar T, Nagalingam B, Gopala Krishan KV. The effect of two ignition improving additives on the performance of jatropha oil in low heat rejection diesel engine. In: 4th international conference on small engines and their fuels, Thailand; 1993. p. 14e9. [110] Agarwal D, Agarwal AK. Performance and emissions characteristics of jatropha oil (preheated and blends) in a direct injection compression ignition engine. Appl Therm Eng 2007;27(13): 2314e23. [111] Hulwan DB, Joshi SV. Performance, emission and combustion characteristic of a multicylinder DI diesel engine running on diesel-ethanol-biodiesel blends of high ethanol content. Appl Energy 2011;88(12):5042e55. [112] Rao PV. Experimental investigations on the influence of properties of jatropha biodiesel on performance, combustion, and emission characteristics of a DI-CI engine. World Acad Sci Eng Technol 2011;5(3):629e42. [113] Senthil Kumar R, Manimaran R. Performance and emission characteristics on 4-stroke single cylinder C. I. Engine using cottonseed bio fuels. Asian J Eng Res 2013. ISSN-2319e2100. [114] Chukwuezie OC, Nwaigwe KN, Asoegwu SN, Anyanwu EE. Diesel engine performance of jatropha biodiesel: a review. Biofuels 2014;5(4):415e30. [115] Bechtsis D, Tsolakis N, Vlachos D, Srai JS. Intelligent autonomous vehicles in digital supply chains: a framework for integrating innovations towards sustainable value networks. J Clean Prod 2018;181:60e71. [116] Lkili C, Aydin H. The harmful effects of diesel engine exhaust emissions. Energy Sources Part A 2012;34(10):899e905. [117] Smith OI. Fundamentals of soot formation in flames with application to diesel engine particulate emissions. Prog Energy Combust Sci 1981;7(4):275e91.
327
[118] Tree DR, Foster DE. Optical measurements of soot particle size, number density, and temperature in a direct injection diesel engine as a function of speed and load. SAE Tech Pap 1994. [119] Pu X, Cai Y, Shi Y, Wang J, Gu L, Tian J, et al. Diesel particulate filter (DPF) regeneration using non-thermal plasma induced by dielectric barrier discharge. J Energy Inst 2017:1e13. [120] Environmental Protection Agency (EPA). Nitrogen oxides (NOx), why and how they are controlled. Epa-456/F-99-006R. 1999. [121] Bady MF, Hassanien HM, Mousa SAS, M Hussein A, ElDean AMK. Study of the effects of using acetic acid in condenser de-scaling on the exhaust emissions and the performance of assiut thermal power plant. J Eng Sci 2013;41(3):971e96. [122] Liberman MA. Combustion and environmental concerns. In: Introduction to physics and chemistry of combustion. Berlin, Heidelberg: Springer; 2008. p. 335e41. [123] Ullman TL. Investigation of the effects of fuel composition on heavy-duty diesel engine emissions. SAE Paper 892072. 1989. [124] Lee R, Pedley J, Hobbs C. Fuel quality impact on heavy duty diesel emissionsda literature review. SAE Paper 982649. 1998. [125] Tree DR, Svensson KI. Soot processes in compression ignition engines. Prog Energy Combust Sci 2007;33:272e309.
Further reading [1] Ejigu A, Asfaw A, Asfaw N, Licence P. Moringa stenopetala seed oil as a potential feedstock for biodiesel production in Ethiopia. Green Chem 2010;12(2):316. [2] Sakai T, Kawashima A, Koshikawa T. Economic assessment of batch biodiesel production processes using homogeneous and heterogeneous alkali catalysts. Bioresour Technol 2009;100(13):3268e76.
III. ENGINE PERFORMANCE, EMISSIONS AND COMBUSTION CHARACTERISTICS